fix FP related to inverted character classes choosing a char that was not matched by the char class

javascript/ql/test/query-tests/Performance/ReDoS/tst.js

@@ -258,3 +258,6 @@ var bad57 = /^([^>a]+)*(>|$)/;
 
 // NOT GOOD
 var bad58 = /(\n\s*)+$/;
+
+// GOOD
+var good26 = /([^\\\]]+)*/