Fix status problem after pulling empty call history

Problem with "OK" status after pulling phonebook for empty call history
(cch) is fixed by this patch. Previously "OK" status was received even
for empty (as it normally does for non-empty) call history and now
"Not Found" status is received in case when there is no call event.

plugins/pbap.c

@@ -251,7 +251,7 @@ static void query_result(const char *buffer, size_t bufsize, int vcards,
 
 	DBG("");
 
-	if (vcards < 0) {
+	if (vcards <= 0) {
 		obex_object_set_io_flags(pbap, G_IO_ERR, -ENOENT);
 		return;
 	}