AnimEncoder: avoid freeing uninitialized memory pointer.

In GenerateCandidates(), when candidate_ll->evaluate_ and
candidate_lossy->evaluate_ are both true, if lossless encoding
exits on error, candidate_ll->evaluate_ would not be correctly
reset. This will cause freeing uninitialized memory pointer in
SetFrame().

BUG=webp:322

Change-Id: I481b49a186e4fa3607ce71b4543a481083edf444
(cherry picked from commit 3ebe1c0003287e1d9b65d99750f227ca7ed4dffc)
1 file changed