happens when decoding is partial (past Partition0), without error and
interrupted by calling WebPIDelete()
WebPIDelete() needs to call VP8ExitCritical() to free in-flight resources
Change-Id: Id4faef1b92f7edd8c17d642c58860e70dd570506
(cherry picked from commit 40ae3520b19e9f2ed22d52b7677d846da8da90de)