api: don't crash /api/forms when there are no formdefs (#32415)

tests/test_api.py

@@ -1863,6 +1863,10 @@ def test_api_global_listing(pub, local_user):
     role = Role(name='test')
     role.store()
 
+    # check there's no crash if there are no formdefs
+    resp = get_app(pub).get(sign_uri('/api/forms/', user=local_user))
+    assert len(resp.json['data']) == 0
+
     FormDef.wipe()
     formdef = FormDef()
     formdef.name = 'test'

wcs/api.py

@@ -217,6 +217,13 @@ class ApiFormsDirectory(Directory):
         self.check_access()
         get_request().user = get_user_from_api_query_string() or get_request().user
 
+        if FormDef.count() == 0:
+            # early return, this avoids running a query against a missing SQL view.
+            get_response().set_content_type('application/json')
+            return json.dumps({'data': []},
+                    cls=misc.JSONEncoder,
+                    encoding=get_publisher().site_charset)
+
         from wcs import sql
 
         management_directory = ManagementDirectory()