ore: Don't crash on NULL bio in _clear_bio

In the case of target returning OSD_ERR_PRI_CLEAR_PAGES when we
only sent for attributes don't crash on NULL bio.
This is an osd-target bug but don't crash regardless
Signed-off-by: NBoaz Harrosh <bharrosh@panasas.com>

fs/exofs/ore.c

@@ -431,8 +431,12 @@ int ore_check_io(struct ore_io_state *ios, ore_on_dev_error on_dev_error)
 		if (likely(!ret))
 			continue;
 
-		if (OSD_ERR_PRI_CLEAR_PAGES == osi.osd_err_pri) {
-			/* start read offset passed endof file */
+		if ((OSD_ERR_PRI_CLEAR_PAGES == osi.osd_err_pri) &&
+		    per_dev->bio) {
+			/* start read offset passed endof file.
+			 * Note: if we do not have bio it means read-attributes
+			 * In this case we should return error to caller.
+			 */
 			_clear_bio(per_dev->bio);
 			ORE_DBGMSG("start read offset passed end of file "
 				"offset=0x%llx, length=0x%llx\n",