WebPPictureImportRGB() can fail on memory allocation. In this case,
jpeg_destroy_decompress() was already called, so do not go to Error.
Free metadata as an error is returned.
Change-Id: I045b072090e9063d3ad10369ad18b0f08bdffe9f
(cherry picked from commit 6e8a4126f2aab78946a5b85045b241707bbe44d2)