Propagate feature to child layers of multi-geometries

Leaflet's geometryToLayer returns a FeatureGroup for MultiPoint, and addData assigns `feature` to that group only. Tooltips resolve their source to the layer that fired the event (Tooltip.js:418, v1.9.3), which is a child marker with no `feature`, so GeoJsonTooltip and GeoJsonPopup throw and never render.

Copy the feature onto child layers in onEachFeature, before any user-supplied callback, so both see the same data.

Fixes #1520

Author: nina-mir

folium/features.py

@@ -586,6 +586,11 @@ class GeoJson(Layer):
         {%- endif %}
 
         function {{this.get_name()}}_onEachFeature(feature, layer) {
+            if (typeof layer.eachLayer === "function") {
+                layer.eachLayer(function (child) {
+                    if (child.feature === undefined) { child.feature = feature; }
+                });
+            }
             {%- if this.on_each_feature %}
             ({{this.on_each_feature}})(feature, layer);
             {%- endif %}