[BUG] Pinch zooming on mobile causes the topological map to turn white

[mgkollander]

Describe the bug
Pinch zooming on mobile can go past the normal zoom limit. The topological tile layer (OpenTopoMap) doesn't display past a certain point, so it switches to the plain white OpenStreetMap tiles by default. This seems to only be an issue with pinch zooming.

Expected behavior
Users shouldn't be able to zoom in close enough for the OpenStreetMap tiles to generate.

Smartphone:

• Device: iPhone 12 Mini
• Browser: Safari

Additional context
Maximum zoom-in value ('maxZoom') does not account for pinch zoom. We have some options:

1. Disable snapping back when at maxZoom
2. Disable pinch zooming-in at maxZoom
3. Push back maxZoom so this can't happen unless someone tries really, really hard