Handle returning nulls from CheckLineOrder correctly. bug=345616 r=smotagu sr=roc

layout/generic/nsFrame.cpp

@@ -4491,14 +4491,18 @@ nsFrame::GetFrameFromDirection(nsPresContext* aPresContext, nsPeekOffsetStruct *
       PRBool isReordered;
       result = it->CheckLineOrder(thisLine, &isReordered, &firstFrame, &lastFrame);
       nsIFrame** framePtr = aPos->mDirection == eDirPrevious ? &firstFrame : &lastFrame;
-      nsBidiLevel embeddingLevel = nsBidiPresUtils::GetFrameEmbeddingLevel(*framePtr);
-      if (((embeddingLevel & 1) && lineIsRTL || !(embeddingLevel & 1) && !lineIsRTL) ==
-          (aPos->mDirection == eDirPrevious)) {
-        GetFirstLeaf(aPresContext, framePtr);
+      if (*framePtr) {
+        nsBidiLevel embeddingLevel = nsBidiPresUtils::GetFrameEmbeddingLevel(*framePtr);
+        if (((embeddingLevel & 1) && lineIsRTL || !(embeddingLevel & 1) && !lineIsRTL) ==
+            (aPos->mDirection == eDirPrevious)) {
+          GetFirstLeaf(aPresContext, framePtr);
+        } else {
+          GetLastLeaf(aPresContext, framePtr);
+        }
+        atLineEdge = *framePtr == traversedFrame;
       } else {
-        GetLastLeaf(aPresContext, framePtr);
+        atLineEdge = PR_TRUE;
       }
-      atLineEdge = *framePtr == traversedFrame;
     } else
 #endif
     {

layout/generic/nsLineBox.cpp

@@ -741,6 +741,8 @@ nsLineIterator::CheckLineOrder(PRInt32                  aLine,
 
   if (!line->mFirstChild) { // empty line
     *aIsReordered = PR_FALSE;
+    *aFirstVisual = nsnull;
+    *aLastVisual = nsnull;
     return NS_OK;
   }
   

layout/tables/nsTableRowGroupFrame.cpp

@@ -1946,6 +1946,8 @@ nsTableRowGroupFrame::CheckLineOrder(PRInt32                  aLine,
                                      nsIFrame                 **aLastVisual)
 {
   *aIsReordered = PR_FALSE;
+  *aFirstVisual = nsnull;
+  *aLastVisual = nsnull;
   return NS_OK;
 }
 #endif // IBMBIDI