[media] cx23885-dvb: check if dvb_attach() succeded

Fix possible null dereference for Leadtek DTV 3200H
XC4000 tuner when no firmware file available.

Cc: [e-mail]
Signed-off-by: Miroslav Slugen <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/video/cx23885/cx23885-dvb.c

···
 
 			fe = dvb_attach(xc4000_attach, fe0->dvb.frontend,
 					&dev->i2c_bus[1].i2c_adap, &cfg);
+			if (!fe) {
+				printk(KERN_ERR "%s/2: xc4000 attach failed\n",
+				       dev->name);
+				goto frontend_detach;
+			}
 		}
 		break;
 	case CX23885_BOARD_TBS_6920: