Only initialize types after #extension directives have been processed.

Since _mesa_glsl_initialize_types add types for various extensions, we
can't call it until after processing "#extension foo : disable" lines.

Fixes tex_rect_02.frag.

glsl_parser_extras.cpp

@@ -737,7 +737,7 @@ main(int argc, char **argv)
 	 ast->print();
       }
 
-      if (!state.translation_unit.is_empty())
+      if (!state.error && !state.translation_unit.is_empty())
 	 _mesa_ast_to_hir(&instructions, &state);
    } else {
       /* FINISHME: We should initialize this to the max GLSL version supported