richedit: Fixed regression in ME_SetCharFormat.

Missed an assignment for end_run when the end cursor is provided and the
end position doesn't cause a split.

dlls/riched20/run.c

@@ -787,6 +787,8 @@ void ME_SetCharFormat(ME_TextEditor *editor, ME_Cursor *start, ME_Cursor *end, C
   {
     end_run = end->pRun = ME_SplitRunSimple(editor, end->pRun, end->nOffset);
     end->nOffset = 0;
+  } else if (end) {
+    end_run = end->pRun;
   }
 
   run = start->pRun;