paride/pcd: need to check if cd->disk is null in pcd_detect

If alloc_disk fails in pcd_init_units, cd->disk & pi are empty, we need
to check if cd->disk is null in pcd_detect.
Reported-by: NHulk Robot <hulkci@huawei.com>
Signed-off-by: Nzhengbin <zhengbin13@huawei.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

drivers/block/paride/pcd.c

@@ -723,9 +723,9 @@ static int pcd_detect(void)
 	k = 0;
 	if (pcd_drive_count == 0) { /* nothing spec'd - so autoprobe for 1 */
 		cd = pcd;
-		if (pi_init(cd->pi, 1, -1, -1, -1, -1, -1, pcd_buffer,
-			    PI_PCD, verbose, cd->name)) {
-			if (!pcd_probe(cd, -1, id) && cd->disk) {
+		if (cd->disk && pi_init(cd->pi, 1, -1, -1, -1, -1, -1,
+			    pcd_buffer, PI_PCD, verbose, cd->name)) {
+			if (!pcd_probe(cd, -1, id)) {
 				cd->present = 1;
 				k++;
 			} else
@@ -736,11 +736,13 @@ static int pcd_detect(void)
 			int *conf = *drives[unit];
 			if (!conf[D_PRT])
 				continue;
+			if (!cd->disk)
+				continue;
 			if (!pi_init(cd->pi, 0, conf[D_PRT], conf[D_MOD],
 				     conf[D_UNI], conf[D_PRO], conf[D_DLY],
 				     pcd_buffer, PI_PCD, verbose, cd->name)) 
 				continue;
-			if (!pcd_probe(cd, conf[D_SLV], id) && cd->disk) {
+			if (!pcd_probe(cd, conf[D_SLV], id)) {
 				cd->present = 1;
 				k++;
 			} else