Release 5.3.1

This release addresses some issues with newer EDDN code which could cause erroneous alerts to the player, or sending of bad messages.

• EDDN: Cope with ApproachSettlement on login occurring before Location, such that we don't yet know the name of the star system the player is in.

  Closes #1484

• EDDN: Cope with ApproachSettlement missing planetary coordinates on login at/near a settlement in Horizons.

  Closes #1476

• EDDN: Change the CodexEntry "empty string" checks to only apply to those values where the schema enforces "must be at least one character".

  This prevents the big 'CodexEntry had empty string, PLEASE ALERT THE EDMC DEVELOPERS' message from triggering on, e.g. NearestDestination being empty, which the schema allows.

  Closes #1481

Plugin Developers

• If you use a sub-class for a widget the core code will no longer break if your code raises an exception. e.g. a plugin was failing due to Python 3.10 using collections.abc instead of collections, and the plugin's custom widget had a configure() method which was called by the core theme code on startup or theme change. This then caused the whole application UI to never show up on startup.

  This also applies if you set up a button such that enter/leave on it, i.e. mouse in/out, causes the theme.py code for that to trigger.

  So, now in such cases the main UI should actually show up, although your plugin's UI might look weird due to theming not being properly applied.

  The plugin exception WILL be logged, at ERROR level.