Fixed #21907 -- Fixed add_srs_entry for Spatialite >= 4

Thanks dfunckt for the report.

django/contrib/gis/utils/srs.py

@@ -64,9 +64,11 @@ def add_srs_entry(srs, auth_name='EPSG', auth_srid=None, ref_sys_name=None,
               }
 
     # Backend-specific fields for the SpatialRefSys model.
-    if connection.ops.postgis:
+    srs_field_names = SpatialRefSys._meta.get_all_field_names()
+    if 'srtext' in srs_field_names:
         kwargs['srtext'] = srs.wkt
-    if connection.ops.spatialite:
+    if 'ref_sys_name' in srs_field_names:
+        # Spatialite specific
         kwargs['ref_sys_name'] = ref_sys_name or srs.name
 
     # Creating the spatial_ref_sys model.