Tile properties panel doesn't update Image Rect limits when image changes #3555

When changing the source image for a tile in an Image Collection, the properties panel remembers the dimensions of the old tile for the Image Rect property, so it's not possible to use the entire tile image if the old image was smaller, and it is possible to set an image rect larger than the new image if the old image was larger. Switching to another tile and then back updates the image rect limits, allowing the subrect to be set correctly.

To Reproduce:

1. Create or open an Image Collection tileset with at least one tile
2. Click on the tile, and change its source Image to one that has different dimensions
3. Try to adjust the image rect to be larger.
4. Notice that you are confined to the old tile's dimensions: if it was smaller, then you can't use the entire image of the new tile, and if it was larger, you can set a subrect larger than the current tile image.

I expect the image rect's limits to be updated immediately when the image is changed, rather than only when the entire properties panel is repopulated.

Encountered on Tiled 1.9.1 (by me) and on Tiled 1.9.2 (by another user).