trace-graph: Test for comm field before using it

The ftrace_comm_field may not be set. Do not use it if
it has not been initialized.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/trace-graph.c b/trace-graph.c
index 04e2439..edd106f 100644
--- a/trace-graph.c
+++ b/trace-graph.c
@@ -1111,7 +1111,7 @@ int trace_graph_check_sched_switch(struct graph_info *ginfo,
 
         if (id == ginfo->ftrace_sched_switch_id) {
                 pevent_read_number_field(ginfo->ftrace_pid_field, record->data, &val);
-                if (comm)
+                if (comm && ginfo->ftrace_comm_field)
                         *comm = record->data + ginfo->ftrace_comm_field->offset;
                 if (pid)
                         *pid = val;