perf: Fix check at end of event search

The original code doesn't work because "call" is never NULL there.
Signed-off-by: Dan Carpenter <error27@gmail.com>
LKML-Reference: <20100320143911.GF5331@bicker>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace_events_filter.c

@@ -1398,7 +1398,7 @@ int ftrace_profile_set_filter(struct perf_event *event, int event_id,
 	}
 
 	err = -EINVAL;
-	if (!call)
+	if (&call->list == &ftrace_events)
 		goto out_unlock;
 
 	err = -EEXIST;