Install Unlisted Engines dialog offers engines that are listed

### What Happened?

After pressing "Install Unlisted Engines" button in the Add Engine popover, a dialog appears offering a selection of Japanese Korean and Chinese input engines. At least some of these e.g. the Japanese Mozc engine were already installed and shown in the list of engines to add. Selecting such an engine and pressing "Install" results in both dialog and popover closing with no feedback and without the selected engine being added to the input method list nor any change being made to the list of available engines.

### Steps to Reproduce

* Open Settings/Keyboard/Input Method
* Open Add Engine dialog (+)
* Search for available Japanese engines
* Note Japanese-Mozc is available
* Click on "Install Unlisted Engines"
* In the dialog select "Japanese"
* Note "ibus-mozc" is listed
* Select and install this
* Note dialog and popover close with feedback nor any change.

### Expected Behavior

Only unlisted engines should be offered in the dialog. After installing an unlisted engine the popover should return with that engine selected.

### OS Version

7.x (Horus)

### Software Version

Latest release (I have run all updates)

### Log Output

_No response_

### Hardware Info

_No response_