Except null as default param value rule of phpstan

rules/phpstan-rules.neon

@@ -5,6 +5,7 @@ parameters:
     ignoreErrors:
         - '#Class (MDMysqliInvalidInput|MDMysqliExpectedError|MDExpectedException|MDgenericInvalidInputsException) is neither abstract nor final.#'
         - '#Method MDMysqli::_check_query_efficiency\(\) is unused.#'
+        - '# with null as default value.#'
     polluteScopeWithLoopInitialAssignments: false
     polluteScopeWithAlwaysIterableForeach: false
     checkAlwaysTrueCheckTypeFunctionCall: true