cid#1606728 Overflowed integer argument

Change-Id: I6fef2b6818018b8a0f82125ef2d8220688d642a3
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/177536
Reviewed-by: Caolán McNamara <caolan.mcnamara@collabora.com>
Tested-by: Jenkins

editeng/source/editeng/editdoc.cxx

@@ -373,7 +373,7 @@ sal_Int32 ParaPortion::GetLineNumber( sal_Int32 nIndex ) const
 
     // Then it should be at the end of the last line!
     DBG_ASSERT(nIndex == maLineList[nCount - 1].GetEnd(), "Index dead wrong!");
-    return (maLineList.Count() - 1);
+    return nCount - 1;
 }
 
 void ParaPortion::CorrectValuesBehindLastFormattedLine( sal_Int32 nLastFormattedLine )