Don't crash if ct_log/2 is called when app not running

src/gm_ctflow.erl

@@ -61,13 +61,19 @@ ct_log(Flow, Fmt, Args) ->
     TS = timestamp(),
     case Flow of
         undefined ->
-            save_log(undefined, TS, Fmt, Args),
+            maybe_save_log_no_flow(TS, Fmt, Args),
             ct:log(Fmt, Args);
         Flow ->
             save_log(Flow, TS, Fmt, Args),
             ct:log("~p[~w]: " ++ Fmt, [Flow, self()|Args])
     end.
-    
+
+maybe_save_log_no_flow(TS, Fmt, Args) ->
+    try save_log(undefined, TS, Fmt, Args)
+    catch
+        error:_ ->
+            ok
+    end.
 
 save_log(Flow, TS, Fmt, Args) ->
     gm_ctflow_log:log(Flow, TS, Fmt, Args).