Add exception handling for #551
Add exception handling for #551

09/07 00:43:07.545: [mme] FATAL: mme_bearer_find_or_add_by_message:
Assertion `sess' failed. (../src/mme/mmecontext.c:2998)

acetcom/nextepc,acetcom/nextepc,acetcom/nextepc,acetcom/nextepc,acetcom/nextepc,acetcom/nextepc,acetcom/nextepc