Try another fix for the GCC warning

That doesn't trigger a Coverity defect this time (CID 470457)

src/sbbs3/umonitor/chat.c

@@ -115,7 +115,7 @@ int chat(scfg_t *cfg, int nodenum, node_t *node, box_t *boxch, void(*timecallbac
 	char	outpath[MAX_PATH];
 	char	usrname[128] = "Unknown user";
 	char	*p;
-	int		ch;
+	uchar	ch;
 	time_t	now;
 	time_t	last_nodechk=0;
 	struct text_info ti;