Fix NPE when uninstalling app

Hey Scott, not sure if this fix is done correctly - but it fixes at least one NPE that sometimes happens when uninstalling an app. Here's the stacktrace of the NPE:

E/AndroidRuntime(23383): FATAL EXCEPTION: main
E/AndroidRuntime(23383): java.lang.NullPointerException
E/AndroidRuntime(23383): 	at com.cyanogenmod.trebuchet.Workspace$12.run(Workspace.java:4362)
E/AndroidRuntime(23383): 	at android.os.Handler.handleCallback(Handler.java:725)
E/AndroidRuntime(23383): 	at android.os.Handler.dispatchMessage(Handler.java:92)
E/AndroidRuntime(23383): 	at android.os.Looper.loop(Looper.java:137)
E/AndroidRuntime(23383): 	at android.app.ActivityThread.main(ActivityThread.java:5235)
E/AndroidRuntime(23383): 	at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime(23383): 	at java.lang.reflect.Method.invoke(Method.java:511)
E/AndroidRuntime(23383): 	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
E/AndroidRuntime(23383): 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
E/AndroidRuntime(23383): 	at dalvik.system.NativeStart.main(Native Method)