Don't throw when toggling a popup or tooltip of a layer that isn't on the map - #10551

layer.togglePopup() and layer.toggleTooltip() throw when the layer isn't on a map, while openPopup() and openTooltip() on the same layer simply do nothing:

const marker = new Marker([0, 0]).bindPopup('Hi');
marker.openPopup();   // no-op
marker.togglePopup(); // TypeError: Cannot read properties of undefined (reading 'hasLayer')

DivOverlay.toggle() calls _prepareOpen() and then opens the overlay on the source layer's map without checking the result. _prepareOpen() returns false when the layer has no map or no overlay source, and Layer.openPopup()/openTooltip() already check that return value before calling openOn(). Without the check, toggle() passes an empty map to openOn(), which throws. For a FeatureGroup with no layers, which is on the map but has no source to anchor the popup to, the popup is still added to the map.

toggle() now only opens the overlay when _prepareOpen() succeeds, the same way openPopup() and openTooltip() do.

Testing

I added specs for toggling a popup on a layer that was removed from the map, toggling a popup bound to an empty FeatureGroup, and toggling a tooltip on a layer that was never added. All three fail on main and pass with this change.

npm test (Chromium) passes with 1396 tests, and npm run lint and npm run typecheck pass.