feat+refactor: trash instance icons

also refactor IconList::deleteIcon

Signed-off-by: leo78913 <leo3758@riseup.net>

launcher/ui/dialogs/IconPickerDialog.cpp

@@ -112,6 +112,9 @@ void IconPickerDialog::addNewIcon()
 
 void IconPickerDialog::removeSelectedIcon()
 {
+    if (APPLICATION->icons()->trashIcon(selectedIconKey))
+        return;
+
     APPLICATION->icons()->deleteIcon(selectedIconKey);
 }