[1.7.x] Fixed #22250 -- regression in gis compiler for non-concrete fields

Thanks to gwahl@fusionbox.com for the report.

Backport of 21f208e6 from master

django/contrib/gis/db/models/sql/compiler.py

@@ -124,7 +124,7 @@ class GeoSQLCompiler(compiler.SQLCompiler):
         seen = self.query.included_inherited_models.copy()
         if start_alias:
             seen[None] = start_alias
-        for field, model in opts.get_fields_with_model():
+        for field, model in opts.get_concrete_fields_with_model():
             if from_parent and model is not None and issubclass(from_parent, model):
                 # Avoid loading data for already loaded parents.
                 continue

django/contrib/gis/tests/geoapp/tests.py

@@ -794,3 +794,12 @@ class GeoQuerySetTest(TestCase):
         self.assertEqual(True, union.equals_exact(u2, tol))
         qs = City.objects.filter(name='NotACity')
         self.assertEqual(None, qs.unionagg(field_name='point'))
+
+    def test_non_concrete_field(self):
+        pkfield = City._meta.get_field_by_name('id')[0]
+        orig_pkfield_col = pkfield.column
+        pkfield.column = None
+        try:
+            list(City.objects.all())
+        finally:
+            pkfield.column = orig_pkfield_col