fix(apis_entities): only set field attributes for existing fields

There is some legacy code that expects specific model fields (the ones
that were part of TempEntityClass). This commit checks if those even
exist, before setting their attributes.

Closes: #298

apis_core/apis_entities/forms.py

@@ -178,10 +178,19 @@ def sort_fields_list(field_names, entity_name):
                     crispy_main_fields, crispy_meta_fields
                 )
             )
-            self.fields["status"].required = False
-            self.fields["collection"].required = False
-            self.fields["start_date_written"].required = False
-            self.fields["end_date_written"].required = False
+            # backwards compatibility:
+            # those fields are part of TempEntityClass - this
+            # block can probably be removed when TempEntityClass
+            # is gone from apis_entities
+            # for now we at least check if they exist
+            if "status" in self.fields:
+                self.fields["status"].required = False
+            if "collection" in self.fields:
+                self.fields["collection"].required = False
+            if "start_date_written" in self.fields:
+                self.fields["start_date_written"].required = False
+            if "end_date_written" in self.fields:
+                self.fields["end_date_written"].required = False
 
             instance = getattr(self, "instance", None)
             if instance != None: