Remove false assertion in ApplyBlockElementCommand::formatSelection()

Source/core/editing/ApplyBlockElementCommand.cpp

Index: Source/core/editing/ApplyBlockElementCommand.cpp
diff --git a/Source/core/editing/ApplyBlockElementCommand.cpp b/Source/core/editing/ApplyBlockElementCommand.cpp
index 938ee5b9abc1f9acbd1163f0e59c3695a3870cdc..c58af8cef1c0ae06bcfc2e61e59d1071658e55fe 100644
--- a/Source/core/editing/ApplyBlockElementCommand.cpp
+++ b/Source/core/editing/ApplyBlockElementCommand.cpp
@@ -146,11 +146,9 @@ void ApplyBlockElementCommand::formatSelection(const VisiblePosition& startOfSel
         if (endAfterSelection.isNotNull() && !endAfterSelection.deepEquivalent().inDocument())
             break;
         // Sanity check: Make sure our moveParagraph calls didn't remove endOfNextParagraph.deepEquivalent().deprecatedNode()
-        // If somehow we did, return to prevent crashes.
-        if (endOfNextParagraph.isNotNull() && !endOfNextParagraph.deepEquivalent().inDocument()) {
-            ASSERT_NOT_REACHED();
+        // If somehow, e.g. mutation event handler, we did, return to prevent crashes.
+        if (endOfNextParagraph.isNotNull() && !endOfNextParagraph.deepEquivalent().inDocument())
             return;
-        }
         endOfCurrentParagraph = endOfNextParagraph;
     }
 }