Reusing an id of a previously removed layer for a layer of a different type causes an error

@mourner is already working on this.

Since May 28, 2020.

Hello I am using mapboxGL.js in an application where we add a fill extrusion layer on a button click. But I get some errors in the console. Here the description and a minimal working example. Thank you so much for your work and time!

**mapbox-gl-js version** : v1.10.1

**browser**: Firefox 76.0.1 but also in Chrome though error description is different.

### Steps to Trigger Behavior
0. Remove the buildings layer
1. Add a fill-extrusion layer of the buildings with the same layer id.
TypeError r is undefined is thrown in the console
2. Remove the fill-extrusion layer
3. Add a fill layer with the same layer Id
TypeError r is undefined is thrown in the console

In my main application I get the **TypeError u is undefined** when removing the fill-extrusion layer and adding a fill layer. I get the **TypeError r is undefined** when removing the fill layer and adding the fill-extrusion layer.
I couldn't reproduce the **TypeError u is undefined** error in the minimal example though.

### Link to Demonstration

https://jsbin.com/keluvefulo/1/edit?html,console,output

Just press the buttons in order to reproduce the error

### Expected Behavior

To not throw errors in the console.

### Actual Behavior

The layer adding and removing works on the map as expected. But I get a lot of errors in the console.