Make model checks safer

If the test database is not set up, this check used to crash when
running manage.py check.

arches/app/models/models.py

@@ -616,7 +616,8 @@ def save(self, *args, **kwargs):
     @classmethod
     def check(cls, **kwargs):
         errors = super().check(**kwargs)
-        errors.extend(cls._check_publication_in_every_language())
+        if kwargs["databases"]:
+            errors.extend(cls._check_publication_in_every_language())
         return errors
 
     @classmethod
@@ -789,7 +790,8 @@ class Meta:
     @classmethod
     def check(cls, **kwargs):
         errors = super().check(**kwargs)
-        errors.extend(cls._check_root_node())
+        if kwargs["databases"]:
+            errors.extend(cls._check_root_node())
         return errors
 
     @classmethod