Add in a missing unlockMutex() on an error path.

Change-Id: I223e64381190184e37a92ce6478340cb7a323e29
diff --git a/cpu_ref/rsCpuScript.cpp b/cpu_ref/rsCpuScript.cpp
index 81e70f0..8186c68 100644
--- a/cpu_ref/rsCpuScript.cpp
+++ b/cpu_ref/rsCpuScript.cpp
@@ -427,6 +427,7 @@
     bcinfo::MetadataExtractor ME((const char *) bitcode, bitcodeSize);
     if (!ME.extract()) {
         ALOGE("Could not extract metadata from bitcode");
+        mCtx->unlockMutex();
         return false;
     }