MapSaver.save() swallows API errors silently

[JeroenDeDauw]

Written by Claude Code, Opus 4.6. Result of code review with @JeroenDeDauw. Context: the Maps extension codebase.

Issue

In resources/MapSaver.js (line 48), .then(paremeters.done) has no .catch() handler. On API failure, the save button disappears (removed before save), no error is shown, and changes are trapped with no way to retry.

Steps to reproduce

1. Start editing GeoJSON on a map
2. Trigger a save when the API is unavailable or returns an error
3. The save button disappears, no error message is shown, and changes cannot be saved

Expected behavior

API errors should be caught and communicated to the user, and the save button should be restored so they can retry.