Remove exception raising in period converter.

period.scm

@@ -82,12 +82,10 @@
 		   (loop (cdr l)
 			 ps
 			 month))
-	       (if (eq? (*member-file-check-syntax*) 'error)
-		   (error 'period-markers->periods "Invalid start/stop sequence marker" marker)
-		   (list #f
-			 (reverse ps)
-			 (sprintf "Invalid start/stop sequence marker ~A" marker)
-			 line-number)))))))
+	       (list #f
+		     (reverse ps)
+		     (sprintf "Invalid start/stop sequence marker ~A" marker)
+		     line-number))))))
 
  ;; Returns duration of period in months. Start is included, end is
  ;; not. The period contains the month just before the specified end.