Creating a std::string with a null pointer is undefined behaviour

headers/modsecurity/rules_set_properties.h

@@ -333,9 +333,9 @@ class RulesSetProperties {
         case FalseConfigBoolean:
             return "False";
         case PropertyNotSetConfigBoolean:
+        default:
             return "Not set";
         }
-        return NULL;
     }
 
 

src/actions/transformations/url_encode.cc

@@ -48,7 +48,7 @@ std::string UrlEncode::url_enc(const char *input,
     len = input_len * 3 + 1;
     d = rval = reinterpret_cast<char *>(malloc(len));
     if (rval == NULL) {
-        return NULL;
+        return {};
     }
 
     /* ENH Only encode the characters that really need to be encoded. */