RMNET control driver sets the device interface pointer to NULL during disconnect and then unlinks the tx URBs. This causes the tx completion handler to get called and access the device interface pointer which is already NULL. Fix the issue by adding a flag which keeps track of device disconnection and do not set device interface pointer to NULL. CRs-Fixed: 373617 Change-Id: I4991c1f437f1ce031c634109aca10e170ca6290b Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>