When I got something like this
ERROR/AndroidRuntime(18677): Caused by: java.lang.NullPointerException
ERROR/AndroidRuntime(18677): at com.companyname.a.a
To retrace back obfuscated ProGuard file do the following steps:
You need to install Proguard.
Proguard provides you with a UI mode which is great tool to retrace.
Open up the proguardgui.sh which you find it in MAC machine
/Users/{name}/Library/Android/sdk/tools/proguard/bin/proguardgui.sh
You can run it through the terminal.