VBA: Macro Error 91 without VBA editor on - no error when it's open

问题

I'm working on a macro that uses the UIAutomationClient client to expand the SAP Analysis ribbon tab from Excel and click one of the buttons available there. This macro is then executed from a Form Control Button.

Here's the code:

'global object to hold the translations
 Dim translations As Object

Public Enum oConditions
  eUIA_NamePropertyId
  eUIA_AutomationIdPropertyId
  eUIA_ClassNamePropertyId
  eUIA_LocalizedControlTypePropertyId
End Enum

'element name translations for English
Function getEnglishTranslations() As Object
  Set Words = CreateObject("Scripting.Dictionary")
  'element, element name
  Words.Add "Analysis", "Analysis"
  Words.Add "Lower Ribbon", "Lower Ribbon"
  Words.Add "Design Panel Group", "Design Panel"
  Words.Add "Design Panel Menu", "Design Panel"
  Words.Add "Display Button", "Display"

  Set getEnglishTranslations = Words
End Function

'element name translations for German
Function getGermanTranslations() As Object
   Set Words = CreateObject("Scripting.Dictionary")

   'element, element name
   Words.Add "Analysis", "Analysis"
   Words.Add "Lower Ribbon", "Unteres Menüband"
   Words.Add "Design Panel Group", "Designbereich"
   Words.Add "Design Panel Menu", "Designbereich"
   Words.Add "Display Button", "Anzeigen"

   Set getGermanTranslations = Words
End Function

Function translate(element As String) As String
    translate = translations(element)
End Function

Sub toggleDisplay()
    Application.ScreenUpdating = False

    Dim oAutomation As New CUIAutomation 'the UI Automation Object
    Dim walker As IUIAutomationTreeWalker
    Set walker = oAutomation.ControlViewWalker
    Dim element As IUIAutomationElement

    'references for elements in the UI tree
    Dim root As IUIAutomationElement
    Dim xl As IUIAutomationElement
    Dim analysisTab As IUIAutomationElement
    Dim xlrib As IUIAutomationElement
    Dim dpanel As IUIAutomationElement
    Dim display As IUIAutomationElement

    'pattern objects which allow the execution of different UI elements' 
    functionality
    Dim oTogglePattern As IUIAutomationTogglePattern
    Dim expcolPattern As IUIAutomationExpandCollapsePattern
    Dim selPattern As IUIAutomationSelectionItemPattern

    'multi-clause condition references to locate the UI elements in the UI 
    tree.
    Dim analysisCond As IUIAutomationCondition
    Dim displayCond As IUIAutomationCondition
    Dim disPanelCond As IUIAutomationCondition

   'stores the language code for the current active language
   Dim languageCode As Integer

   'get the active application language
   languageCode = _
   Application.International(XlApplicationInternational.xlCountryCode)

   'choose the language dictionary based on the active language
   If languageCode = 49 Then
       Set translations = getGermanTranslations
   Else
       Set translations = getEnglishTranslations
   End If

   'get a reference to the UI element tree
   Set root = oAutomation.GetRootElement

   'locate the Excel window
   Set xl = root.FindFirst(TreeScope_Descendants, PropCondition(oAutomation, 
   eUIA_NamePropertyId, _
   "test wb for hidden ribbon - new (delete me).xlsm - Excel"))

   'click the Analysis tab
   Set analysisCond = _ 
   oAutomation.CreateAndCondition(PropCondition(oAutomation, 
   eUIA_NamePropertyId, translate("Analysis")), _
   PropCondition(oAutomation, eUIA_ClassNamePropertyId, "NetUIRibbonTab"))
   Set analysisTab = xl.FindFirst(TreeScope_Descendants, analysisCond)
   Set selPattern = _ 
   analysisTab.GetCurrentPattern(UIA_SelectionItemPatternId)
   selPattern.Select

   'locate the Design Panel Group
   Set xlrib = xl.FindFirst(TreeScope_Descendants, 
   PropCondition(oAutomation, eUIA_NamePropertyId, translate("Lower 
   Ribbon")))

   Set dpanel = xlrib.FindFirst(TreeScope_Descendants, 
   PropCondition(oAutomation, eUIA_NamePropertyId, translate("Design Panel 
   Group")))

   'try locating the Display button
   Set displayCond = _ 
   oAutomation.CreateAndCondition(PropCondition(oAutomation, 
   eUIA_NamePropertyId, translate("Display Button")), _
   PropCondition(oAutomation, eUIA_ClassNamePropertyId, 
   "NetUIRibbonButton"))

   Set display = dpanel.FindFirst(TreeScope_Descendants, displayCond)

   'true when the window is shrunk to a point where the display button
   'is part of the dropdown menu under Design Panel
   If display Is Nothing Then

       'expand the Design Panel dropdown first
       Set disPanelCond = _ 
       oAutomation.CreateAndCondition(PropCondition(oAutomation, 
       eUIA_NamePropertyId, translate("Design Panel Menu")), _

       PropCondition(oAutomation, eUIA_ClassNamePropertyId, "NetUIAnchor"))
       Set dpanel = dpanel.FindFirst(TreeScope_Descendants, disPanelCond)
       Set expcolPattern = _ 
       dpanel.GetCurrentPattern(UIA_ExpandCollapsePatternId)
       expcolPattern.Expand

      'attempt to locate the Display button again
      Set display = dpanel.FindFirst(TreeScope_Descendants, displayCond)
   End If

   'Click the Display button programmatically (FINALLY!!!)
   Set oTogglePattern = display.GetCurrentPattern(UIA_TogglePatternId)
   oTogglePattern.Toggle

   Application.ScreenUpdating = True
End Sub

'generate a Condition object with the string to be matched against the 
selected property
Function PropCondition(UiAutomation As CUIAutomation, Prop As oConditions, 
Requirement As String) As IUIAutomationCondition
Select Case Prop
    Case 0
          Set PropCondition = _
          UiAutomation.CreatePropertyCondition(UIA_NamePropertyId, 
          Requirement)
    Case 1
          Set PropCondition = _ 
          UiAutomation.CreatePropertyCondition(UIA_AutomationIdPropertyId, 
          Requirement)
    Case 2
          Set PropCondition = _
          UiAutomation.CreatePropertyCondition(UIA_ClassNamePropertyId, 
          Requirement)
    Case 3
          Set PropCondition = _ 
          UiAutomation.CreatePropertyCondition(UIA_ClassNamePropertyId, 
          Requirement)
    End Select
End Function

I have this strange issue that I cannot find the origin for, but I'm able to reproduce it consistently. Every time I click on the button without having the VBA editor opened, I get run time error 91.

This is the line on which the error occurs - analysisTab refers to Nothing which means it wasn't set for some reason.

I would appreciate it if you can help me spot the cause of this annoying problem.

来源：https://stackoverflow.com/questions/57711269/vba-macro-error-91-without-vba-editor-on-no-error-when-its-open