fix(spp_gis): null draw control before destroying map on re-render

When renderMap() destroys the old map, the MapboxDraw control's
internal map reference becomes null. Later, addDrawInteraction()
tried to removeControl(this.draw) from the new map, but the draw
control called this.map.off() on its now-null internal reference.

Fix: set this.draw = null before map.remove() so addDrawInteraction
skips the removeControl call for stale controls.

Author: jeremi

spp_gis/static/src/js/widgets/gis_edit_map/field_gis_edit_map.esm.js

@@ -133,6 +133,7 @@ export class FieldGisEditMap extends Component {
         }
 
         if (this.map) {
+            this.draw = null;
             this.map.remove();
         }