Replace one more occurrence of -1 with PIX_FMT_NONE. Fixes icc warning #188: enumerated type mixed with another type 
Replace one more occurrence of -1 with PIX_FMT_NONE.
Fixes icc warning #188: enumerated type mixed with another type 


git-svn-id: a4d7c1866f8397a4106e0b57fc4fbf792bbdaaaf@13136 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

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