gbproxy: Fix segfault when receiving PAGING for unknown destination

The 'nse' variable had been used both as the input argument of the
SGSN-side NSE, as well as a loop iteration variable.  Let's separate
this clearly.

Closes: OS#4904
Change-Id: I375a219cd72eb11a9a0cb7d55a3efb7b83b771ac
1 file changed