[automerger skipped] Merge "Fix potential NPE while releasing worker thread of ImageWallpaper" into qt-qpr1-dev am: 85fc58ae81 -s ours

am skip reason: Change-Id I243274af54538fc89268c448aa2c5a95f63c7ae3 with SHA-1 4e4044060e is in history

Change-Id: I54834c769ec5aa2b6b98a94ac57db1701f797388