Correction

src/Entity/Db/ProcessStep.php

@@ -93,13 +93,13 @@ class ProcessStep
         return $this;
     }
 
-    public function setLabel($label) :ProcessStep {
+    public function setLabel(?string $label): ?string {
         $this->label = $label;
 
         return $this;
     }
 
-    public function getLabel() :string {
+    public function getLabel(): ?string {
         return $this->label;
     }