Avoid infinite loop in case system_server does not have delete access.

This must not ever happen, but if it does then let's crash with a good
error message instead of hanging and getting out of stack memory
exception.

Bug: 269072872
Test: atest ShortcutManagerTest1
Change-Id: I7e4d9ac612c9e4e45d1521e3bebfb787fe21c953