Decoder: Fixes for handling errors in multi-slice MB Aff streams Initialize default reference buffer for erroneous interlaced clips Pick slice_type from decode thread slice structure Call start_of_pic only once Bug: 30822755 Change-Id: I553c646446d99a626d62351aa1b385355191cdc3 (cherry picked from commit bc71ad2d43dc03b2a71e3423da5385ed3cb9799a)