Bug 1163878 (Followup) - Fix a warning about implicit conversion of nullptr to bool in FrameLayerBuilder on a CLOSED TREE. r=me

--HG--
extra : amend_source : 0f707d08439edf2f1e8e229d4cec501964c12f65

layout/base/FrameLayerBuilder.cpp

@@ -2375,7 +2375,7 @@ bool
 PaintedLayerData::CanOptimizeToImageLayer(nsDisplayListBuilder* aBuilder)
 {
   if (!mImage) {
-    return nullptr;
+    return false;
   }
 
   return mImage->CanOptimizeToImageLayer(mLayer->Manager(), aBuilder);