Only execute clear_blocks() when needed. +0.3% speedup for both aladin & cathedral.
Only execute clear_blocks() when needed.
+0.3% speedup for both aladin & cathedral.


git-svn-id: a4d7c1866f8397a4106e0b57fc4fbf792bbdaaaf@16252 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

prajnashi/ffmpeg,prajnashi/ffmpeg,prajnashi/ffmpeg,prajnashi/ffmpeg