Fix for inverted character class ranges

src/re.cpp

@@ -187,7 +187,9 @@ namespace lxs {
                 }
                 else
                 {
+                    if (idx < end - 1 && input[idx + 1] != '-')
                         used_chars.insert(input[idx]);
+                    else
                         last_char = input[idx];
                 }
             }