diff --git a/src/TypesGenerator.php b/src/TypesGenerator.php
index <HASH>..<HASH> 100644
--- a/src/TypesGenerator.php
+++ b/src/TypesGenerator.php
@@ -258,7 +258,7 @@ class TypesGenerator
                     }
 
                     foreach ($this->getParentClasses($type) as $typeInHierarchy) {
-                        foreach ($propertiesMap[$typeInHierarchy->getUri()] as $property) {
+                        foreach ($propertiesMap[$typeInHierarchy->getUri()] ?? [] as $property) {
                             if ($key !== $property->localName()) {
                                 continue;
                             }
fix: Check if key is set to prevent warning (#<I>)

* fix: Check if key is set to prevent warning



When the properitesMap array gets iterated to generate the fields, it happens that the uri of the typeInHierarchy is not a key of the said array; this triggers a PHP Warning:  Undefined array key. Seems to happen only for custom classes definition though. This does not prevent the command to run, this is really not critical.



* Update src/TypesGenerator.php