USB: cdc-acm: Fix stupid NULL pointer in resume()

Stupid logic bug passing a just nulled pointer

Signed-off-by: Oliver Neukum <neukum@b1-systems.de>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 975d556..be6331e 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -1441,7 +1441,7 @@
 			wb = acm->delayed_wb;
 			acm->delayed_wb = NULL;
 			spin_unlock_irq(&acm->write_lock);
-			acm_start_wb(acm, acm->delayed_wb);
+			acm_start_wb(acm, wb);
 		} else {
 			spin_unlock_irq(&acm->write_lock);
 		}