Fixing canvas resizing

If the pixel size is too big and the canvas size is changed, the canvas will have a very big size to the point where the editor can no longer be used and have to be restarted.

Reproduce the issue in the pixel art editor by using a large pixel size and changing the canvas size. Trace where canvas resizing is handled and determine why the editor becomes unusable. Done means changing the canvas size keeps the editor usable without requiring a restart.

Written by the indexing model from the issue text.