Fixing NULL pointer access causing segmentation fault in aapt

In cases where resource packages are generated which does
not have public resources for all resource types - NULL
pointers sneaks into the mOrderedConfigs vector causing
the aapt tool to crash. The solution in this fix simply
ignores the NULL elements when later processing the sorted
vector.

The NULL elements are inserted during applyPublicEntryOrder
function call

Change-Id: I8b7135932e2d235018da2e2f7e09f0d22f1b2f59
Framework/base: Added synchronization block to avoid race condition

Fix for the synchronization issue leading to access of an array
Index out of bounds. Issue occurs due to race condition between
removing the activities of a crashed process from history stack
and resuming a separate activity.

Change-Id: I14bb5834e778c15b674248e46fe93b0ce9f37967