fsm: guard action callback

The FSM allows to set individual action callback functions for each
state but it does not allow to leave the action callback pointer
unpopulated. However, there are cornercases where having no callback
function is desirable.

- Check if action callback is popolated before executing it.

Change-Id: I36d221c973d3890721ef1d376fb9be82c4311378

1 files changed, 3 insertions, 1 deletions

diff --git a/src/fsm.c b/src/fsm.c
index ae2fdc2a..0370f65e 100644
--- a/src/fsm.c
+++ b/src/fsm.c
@@ -541,7 +541,9 @@ int _osmo_fsm_inst_dispatch(struct osmo_fsm_inst *fi, uint32_t event, void *data
 			    osmo_fsm_event_name(fsm, event));
 		return -1;
 	}
-	fs->action(fi, event, data);
+
+	if (fs->action)
+		fs->action(fi, event, data);
 
 	return 0;
 }