Fix NullPointerException thrown by logging

When `properties` is null, this propagates a NullPointerException back
to the caller instead of cleanly reporting null like it's supposed to.

Issue introduced in Iec7ba6fc59912f44341fbe8d7f99193b9ead52f0 from the
start of this function and is fixed by just printing `object` instead
of `object.toString()`.

Test: atest AssistIntentConditionalTest
Bug: 158682298
Change-Id: Ic64f6fba65895e9facc9994f5d1a353081ab3253