Fix for inverted character class ranges

src/re.cpp

@@ -187,8 +187,10 @@ namespace lxs {
                 }
                 else
                 {
-                    used_chars.insert(input[idx]);
+                    if (idx < end - 1 && input[idx + 1] != '-')
-                    last_char = input[idx];
+                        used_chars.insert(input[idx]);
+                    else
+                        last_char = input[idx];
                 }
             }