sgsn_mm_ctx_find_ggsn_ctx(): fix: always set gsm_cause

GCC 9 complains that variable 'gsm_cause' in do_act_pdp_req() may
be uninitialized. This may happen if sgsn_mm_ctx_find_ggsn_ctx()
would return NULL due to no static GGSN configured.

Change-Id: I09c608045dd35b9898b82e236a306ab9a6c2c0b9
1 file changed