Fix/settings

[redrathnure]

Fix application settings saving and restoring.

It fixes #777 and was mentioned in #768

Pull Request type

Please check the type of change your PR introduces:

• Bugfix
• [] Feature
• [] Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• [] Build-related changes
• [] Documentation content changes
• [] Other (please describe):

What is the current behavior?

• some of settings (e.g. font size) are not restored between run sessions
• sweep configuration is not saved between run sessions
• app crashes right before exit

Issue Number: 777

What is the new behavior?

settings are saved on exit and restored on app start

Does this introduce a breaking change?

• [] Yes
• No

Other information

[zarath]

Many thanks1