修正多段线倒角在起点是圆弧时发现的错误

src/Add-on/Fillet.ts

@@ -379,7 +379,9 @@ export class CommandFillet implements Command
             }
             else//首尾
             {
+                let oldBul = pln.GetBuilgeAt(0);
                 pln.StartPoint = sp;
+                pln.SetBulgeAt(0, oldBul);
                 let plPtCount = pln.NumberOfVertices;
                 if (pln.EndParam === plPtCount)//CloseMark
                 {