Backport of "assrender: Don't try unlocking unlocked mutex" into 1.18
requested to merge tpm/gst-plugins-bad:backport-mr-1918-into-1.18-assrender-dont-unlock-unlocked-mutex into 1.18
Backport of !1918 (merged) "assrender: Don't try unlocking unlocked mutex".
Commits:
- b258144c assrender: Don't try unlocking unlocked mutex