gprs_gmm.c: Don't try to de-reference NULL mmctx
There was a comment in the code that certain GMM messages require a
valid mmctx pointer. However, nothing actually checked if that pointer
was in fact non-NULL. We plainly crashed if a MS would send us the
wrong message in the wrong state.
Original patch by Harald Welte, but it broke message validity checking,
resulting in sgsn_test failure. This re-implements the NULL check in a
different way, as explained by in-code comment.
Change-Id: I7908de65bec91599f7042549b832cbbd7ae5a9a8
1 file changed