The grant handle must be invalidated only in the error path.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

--- a/drivers/xen/blktap2/device.c
+++ b/drivers/xen/blktap2/device.c
@@ -516,8 +516,8 @@ blktap_map_foreign(struct blktap *tap,
 				WARN_ON(table->grants[grant].status == GNTST_eagain);
 				BTERR("invalid user buffer: could not remap it\n");
 				err |= 1;
+				table->grants[grant].handle = INVALID_GRANT_HANDLE;
 			}
-			table->grants[grant].handle = INVALID_GRANT_HANDLE;
 			request->handles[i].user = table->grants[grant].handle;
 			grant++;
 		}