Removing all characters from the search field does not reset listview

[michaelschattgen]

While I was reviewing and testing #1505 I found out that our search doesn't refresh the entry list after removing all characters from a applied searchfilter. Steps to reproduce:

1. Open Aegis and unlock the vault
2. Tap the search icon
3. Search for an entry and apply the search filter (press the magnifiying glass on the keyboard)
4. Tap the search icon again
5. Remove all characters from the search field

Not all entries are shown and the searchfilter actually has the last character that was available in the search field applied.