Fix METADATA_BLOCK_PICTURE check for all-0 params.
Fix METADATA_BLOCK_PICTURE check for all-0 params.

width=height=depth=colors=0 should be allowed, but wasn't thanks to
 some missing parentheses.
Thanks to Lithopsian for the report.

SmartWalkieOrg/opusfile,SmartWalkieOrg/opusfile,xiph/opusfile,youfearm3/opusfile,xiph/opusfile,xiph/opusfile,SmartWalkieOrg/opusfile,youfearm3/opusfile