Crash when importing if PreferencesFragment is restored from instance state

[alexbakker]

When importing, the app crashes if the PreferencesFragment is restored from instance state after selecting the file to import. This can easily be reproduced by enabling "Don't keep activities" in developer options and trying to use the import function in Aegis.

This happens because the following three fields are not restored:

Aegis/app/src/main/java/com/beemdevelopment/aegis/ui/PreferencesFragment.java

Lines 84 to 86 in 626995e

	private Class<? extends DatabaseImporter> _importerType;
	private AegisImporter.State _importerState;
	private UUIDMap<VaultEntry> _importerEntries;