glamr/search: fix crash on full text search coming from certain pages

Some, e.g. FilteredListView /filter/uniref100/, model-based views with
SearchFormMixin where the model is not one of the blessed searchable
ones, so e.g. UniRef100, that non-searchable model was passed to the
search_result view giving a 404 since invalid model.

The fix puts the "global search" placeholder as the model parameter in
those cases.

mibios/glamr/views.py

@@ -907,12 +907,12 @@ def get_context_data(self, **ctx):
         ]
 
         search_model = self.search_model or self.model
-        if search_model in [self.ANY_MODEL, None]:
-            ctx['search_model'] = None
-            ctx['search_model_name'] = self.ANY_MODEL_URL_PART
-        else:
+        if search_model in self.model_class.values():
             ctx['search_model'] = search_model
             ctx['search_model_name'] = search_model._meta.model_name
+        else:
+            ctx['search_model'] = None
+            ctx['search_model_name'] = self.ANY_MODEL_URL_PART
         return ctx