[28902] Don't fail hard on missing CF date

https://community.openproject.com/wp/28902

app/models/custom_actions/actions/strategies/date.rb

@@ -38,7 +38,10 @@ module CustomActions::Actions::Strategies::Date
   end
 
   def apply(work_package)
-    work_package.send("#{self.class.key}=", date_to_apply)
+    accessor = :"#{self.class.key}="
+    if work_package.respond_to? accessor
+      work_package.send(accessor, date_to_apply)
+    end
   end
 
   private