[automerger skipped] Merge "Fix potential NPE while releasing worker thread of ImageWallpaper" into qt-qpr1-dev am: 85fc58ae -s ours am: 8f267e43 -s ours am: f87d987a -s ours am: 94a3a090 -s ours

am skip reason: Change-Id I243274af54538fc89268c448aa2c5a95f63c7ae3 with SHA-1 4e404406 is in history

Change-Id: I700baedd47741ee4c2df36e54ccde1aa2df0d5b4