Flatpak app crashes after attempting to add an account

OS: OpenSUSE Leap 15.4
DE: KDE 5.24.4
Flatpak version: 1.12.5

After hitting "Save" when on the Add Accounts page, the app entirely crashes.

```
# flatpak run com.github.muriloventuroso.easyssh

** (com.github.muriloventuroso.easyssh:2): CRITICAL **: 16:58:18.359: file ../src/MainWindow.vala: line 233: uncaught error: Failed to execute child process “xdg-mime” (No such file or directory) (g-exec-error-quark, 8)

(com.github.muriloventuroso.easyssh:2): Gtk-CRITICAL **: 16:58:22.233: gtk_widget_get_style_context: assertion 'GTK_IS_WIDGET (widget)' failed

(com.github.muriloventuroso.easyssh:2): Gtk-CRITICAL **: 16:58:22.233: gtk_style_context_add_class: assertion 'GTK_IS_STYLE_CONTEXT (context)' failed

(com.github.muriloventuroso.easyssh:2): Gtk-CRITICAL **: 16:58:22.233: gtk_container_add: assertion 'GTK_IS_WIDGET (widget)' failed

(com.github.muriloventuroso.easyssh:2): Json-WARNING **: 16:58:34.592: Unsupported type `gpointer'

(com.github.muriloventuroso.easyssh:2): Json-WARNING **: 16:58:34.593: Unsupported type `gpointer'

(com.github.muriloventuroso.easyssh:2): Json-WARNING **: 16:58:34.593: Unsupported type `gpointer'

(com.github.muriloventuroso.easyssh:2): Json-WARNING **: 16:58:34.593: Unsupported type `gpointer'

(com.github.muriloventuroso.easyssh:2): Json-WARNING **: 16:58:34.593: Unsupported type `gpointer'

(com.github.muriloventuroso.easyssh:2): Json-WARNING **: 16:58:34.593: Unsupported type `gpointer'

(com.github.muriloventuroso.easyssh:2): Json-WARNING **: 16:58:34.593: Unsupported type `gpointer'

(com.github.muriloventuroso.easyssh:2): Json-WARNING **: 16:58:34.593: Unsupported type `gpointer'

(com.github.muriloventuroso.easyssh:2): Json-WARNING **: 16:58:34.594: Unsupported type `gpointer'

(com.github.muriloventuroso.easyssh:2): Json-WARNING **: 16:58:34.594: Unsupported type `gpointer'

(com.github.muriloventuroso.easyssh:2): Json-WARNING **: 16:58:34.594: Unsupported type `gpointer'

(com.github.muriloventuroso.easyssh:2): Json-WARNING **: 16:58:34.594: Unsupported type `gpointer'

(com.github.muriloventuroso.easyssh:2): Json-WARNING **: 16:58:34.594: Unsupported type `gpointer'

(com.github.muriloventuroso.easyssh:2): Json-WARNING **: 16:58:34.594: Unsupported type `gpointer'
```

Reproduce the crash with `flatpak run com.github.muriloventuroso.easyssh` and inspect `src/MainWindow.vala` at line 233. Focus on the failed `xdg-mime` execution and the account-save path, then verify that saving an account no longer terminates the app on the reported Flatpak environment.

Written by the indexing model from the issue text.