开发:避免错误

src/Add-on/DrawDim/DimArc.ts

@@ -11,7 +11,8 @@ import { HotCMD } from "../../Hot/HotCommand";
 
 function GetBoardCurve(ent: Board): Arc | undefined
 {
-    return GetPolylineArc(ent.ContourCurve.Clone().ApplyMatrix(ent.OCSNoClone) as Polyline);
+    if (ent.ContourCurve instanceof Polyline)
+        return GetPolylineArc(ent.ContourCurve.Clone().ApplyMatrix(ent.OCSNoClone) as Polyline);
 }
 
 function GetPolylineArc(cu: Polyline)