Fixes NPE when calling getPackage on a null shortcut

Test: atest com.android.server.pm.ShortcutManagerTest1 \
            com.android.server.pm.ShortcutManagerTest2 \
            com.android.server.pm.ShortcutManagerTest3 \
            com.android.server.pm.ShortcutManagerTest4 \
            com.android.server.pm.ShortcutManagerTest5 \
            com.android.server.pm.ShortcutManagerTest6 \
            com.android.server.pm.ShortcutManagerTest7 \
            com.android.server.pm.ShortcutManagerTest8 \
            com.android.server.pm.ShortcutManagerTest9 \
            com.android.server.pm.ShortcutManagerTest10
Test: Launcher tests pass
Bug: 148869137

Change-Id: Idf27108e6b40106f4604bb5fa9d8061b5b8ce8be