staging: wlags49_h2: Fixes the sparse warning in sta_h2.c

This patch fixes sparse warning "Using plain integer as NULL pointer" in
sta_h2.c

Signed-off-by: Archana kumari <archanakumari959@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>