Fix broken arc drawing in Camera app.

Commit f311e1983741e71e1632044bc8b2356d8688d29c introduced a recursion
abortion threshold, but missed properly handling negative values. Fixit.

Change-Id: I6776371d1567eba0a84d2e1bf702b46879e30332
(cherry picked from commit 37e22b2e5678bcaf66c00c0a9c15baf90e36ee17)