Avoid out-of-bounds issue 
Avoid out-of-bounds issue 

When accessing to reference vector list with NONE_FRAME

BUG=aomedia:412

Change-Id: I82a23591d6d9a179eb6f3b1e40f8d1f4018a53d8

GrokImageCompression/aom,smarter/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,smarter/aom,smarter/aom,GrokImageCompression/aom,smarter/aom,smarter/aom,smarter/aom