Don't split inlines with bidi-isolated kids unnecessarily when they don't have siblings. Bug 793233, r=roc, a=lsblakk

layout/base/nsBidiPresUtils.cpp

@@ -872,9 +872,10 @@ nsBidiPresUtils::ResolveParagraph(nsBlockFrame* aBlockFrame,
       if (child) {
         parent = child->GetParent();
         if (parent && IsBidiSplittable(parent)) {
-          // no need to null-check the result of GetPrevSibling, because
-          // SplitInlineAncestors accepts a null parameter
-          SplitInlineAncestors(parent, child->GetPrevSibling());
+          nsIFrame* prev = child->GetPrevSibling();
+          if (prev) {
+            SplitInlineAncestors(parent, prev);
+          }
         }
       }
     }