Fix: A vector layer can be spatial but having symbology disabled

The fix #591 has been done in `duplicated_rule_key_legend` for "categorizedSymbol", "RuleRenderer", "graduatedSymbol" renderer type.

It has not been done in `duplicated_label_legend` for "RuleRenderer" renderer type.

Funded by WPD Onshore France

Author: rldhont

lizmap/project_checker_tools.py

@@ -531,6 +531,10 @@ def duplicated_label_legend(project: QgsProject, filter_data: bool = True) -> Di
             continue
 
         renderer = layer.renderer()
+        if not renderer:
+            # https://github.com/3liz/lizmap-plugin/issues/591
+            # A vector layer can be spatial but having symbology disabled
+            continue
 
         # From QGIS source code :
         # https://github.com/qgis/QGIS/blob/71499aacf431d3ac244c9b75c3d345bdc53572fb/src/core/symbology/qgsrendererregistry.cpp#L33