No value provided for variable {TileMatrix}

Nobody has claimed this yet.

With leaflet

"leaflet": "^1.9.3",
"leaflet-image": "^0.4.0",

in my package.json (the values I get from `npm install leaflet-image`), and the following code:

var map = L.map("towMap", {
preferCanvas: true,
layers: [
baseLayer,
towTrack,
sampleLayer
] })
leafletImage(map, function (err, canvas) {
...

I get the error
```
No value provided for variable {TileMatrix}
```
baseLayer is from `L.GIBSLayer` (gibs-leaflet package), so perhaps is not CORS-compliant as required (I have no idea how to test that), but if that's the case the error message could be more obvious.

Start with the leafletImage(map, callback) entry point and reproduce the error using leaflet 1.9.3, leaflet-image 0.4.0, and an L.GIBSLayer base layer. Trace where the {TileMatrix} value is required and determine whether the layer or CORS behavior causes the failure. Done means the cause is confirmed and the resulting error is made more informative, if appropriate.

Written by the indexing model from the issue text.