From c0a28dbd30a65ff511dd5ba98b17fb2d7d0c65ac Mon Sep 17 00:00:00 2001
From: Jonathan Kew <jkew@mozilla.com>
Date: Fri, 6 Dec 2019 13:42:37 +0100
Subject: [PATCH] Check if we're already at the end of the frame's content.

---
 layout/generic/nsTextFrame.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/layout/generic/nsTextFrame.cpp b/layout/generic/nsTextFrame.cpp
index 0641c7439a..59ef020ce2 100644
--- a/layout/generic/nsTextFrame.cpp
+++ b/layout/generic/nsTextFrame.cpp
@@ -7525,7 +7525,8 @@ nsTextFrame::GetCharacterRectsInRange(int32_t aInOffset,
       gfxSkipCharsIterator nextIter(iter);
       nextIter.AdvanceOriginal(1);
       if (!nextIter.IsOriginalCharSkipped() &&
-          !mTextRun->IsClusterStart(nextIter.GetSkippedOffset())) {
+          !mTextRun->IsClusterStart(nextIter.GetSkippedOffset()) &&
+          nextIter.GetOriginalOffset() < kContentEnd) {
         FindClusterEnd(mTextRun, kContentEnd, &nextIter);
       }