drivers/gps: fix segfault when parsing arguments

running gps command without parameters results in segfault
due to illegal access to unallocated memory

Signed-off-by: Nicolae Rosia <nicolae.rosia@gmail.com>

src/drivers/gps/gps.cpp

@@ -631,6 +631,10 @@ gps_main(int argc, char *argv[])
 	bool fake_gps = false;
 	bool enable_sat_info = false;
 
+	if (argc < 2) {
+		goto out;
+	}
+
 	/*
 	 * Start/load the driver.
 	 */