[media] dib8000: move dereference after check for NULL

My static checker complains that we dereference "state" inside the call
to fft_to_mode() before checking for NULL.  The comments say that it is
possible for "state" to be NULL so I have moved the dereference after
the check.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/dvb/frontends/dib8000.c

@@ -2680,12 +2680,14 @@ static int dib8000_tune(struct dvb_frontend *fe)
 {
 	struct dib8000_state *state = fe->demodulator_priv;
 	int ret = 0;
-	u16 lock, value, mode = fft_to_mode(state);
+	u16 lock, value, mode;
 
 	// we are already tuned - just resuming from suspend
 	if (state == NULL)
 		return -EINVAL;
 
+	mode = fft_to_mode(state);
+
 	dib8000_set_bandwidth(fe, state->fe[0]->dtv_property_cache.bandwidth_hz / 1000);
 	dib8000_set_channel(state, 0, 0);