【fix】 【注释】右键页面上的签名注释，必现崩溃

PDF Office/PDF Master/Class/PDFWindowController/PDFListView/CPDFListViewExtension/CPDFListView+Event.m

@@ -790,7 +790,9 @@ static inline CPDFAreaOfInterest CAreaOfInterestForResizeHandle(CRectEdges mask,
                 [menu insertItem:cutItem atIndex:0];
             }
             if ([self.activeAnnotation isKindOfClass:[CPDFSignatureAnnotation class]]) {
-                [menu insertItem:pasteItem atIndex:0];
+                if ([menu.itemArray containsObject:pasteItem] == false) {
+                    [menu insertItem:pasteItem atIndex:0];
+                }
             }
             [menu insertItem:copyItem atIndex:0];