fix phpstan deprecation warning (#2023)

Author: smhg

phpstan.neon

@@ -2,11 +2,12 @@ includes:
     - phpstan-baseline.neon
 parameters:
     level: 7
-    checkMissingIterableValueType: false
     reportUnmatchedIgnoredErrors: false
     paths:
         - '%rootDir%/../../../src/'
     ignoreErrors:
         - '#Call to an undefined method .+Collection::.+Array\(\)#'
         - '#Call to an undefined method object::.+\(\)#'
+        -
+            identifier: missingType.iterableValue