[media] dib0090: do the right thing if rf_ramp is NULL

As warned by smatch:
	drivers/media/dvb-frontends/dib0090.c:1118 dib0090_pwm_gain_reset() error: we previously assumed 'state->rf_ramp' could be null (see line 1086)
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/dvb-frontends/dib0090.c

@@ -1115,9 +1115,15 @@ void dib0090_pwm_gain_reset(struct dvb_frontend *fe)
 		dib0090_set_bbramp_pwm(state, bb_ramp);
 
 		/* activate the ramp generator using PWM control */
-		dprintk("ramp RF gain = %d BAND = %s version = %d", state->rf_ramp[0], (state->current_band == BAND_CBAND) ? "CBAND" : "NOT CBAND", state->identity.version & 0x1f);
-
-		if ((state->rf_ramp[0] == 0) || (state->current_band == BAND_CBAND && (state->identity.version & 0x1f) <= P1D_E_F)) {
+		if (rf_ramp)
+			dprintk("ramp RF gain = %d BAND = %s version = %d",
+				state->rf_ramp[0],
+				(state->current_band == BAND_CBAND) ? "CBAND" : "NOT CBAND",
+				state->identity.version & 0x1f);
+
+		if (rf_ramp && ((state->rf_ramp[0] == 0) ||
+		    (state->current_band == BAND_CBAND &&
+		    (state->identity.version & 0x1f) <= P1D_E_F))) {
 			dprintk("DE-Engage mux for direct gain reg control");
 			en_pwm_rf_mux = 0;
 		} else