[1.5.x] Made gis get_default_columns mirror changes in normal compiler

The copy-pasted part of gis compiler's get_default_columns wasn't
changed to match changes in a0155f3534.

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

@@ -119,14 +119,16 @@ class GeoSQLCompiler(compiler.SQLCompiler):
         result = []
         if opts is None:
             opts = self.query.model._meta
-        # Skip all proxy to the root proxied model
-        opts = opts.concrete_model._meta
         aliases = set()
         only_load = self.deferred_to_columns()
 
         if start_alias:
             seen = {None: start_alias}
         for field, model in opts.get_fields_with_model():
+            # For local fields (even if through proxy) the model should
+            # be None.
+            if model == opts.concrete_model:
+                model = None
             if local_only and model is not None:
                 continue
             if start_alias: