Fixed logic error in book_append_sheet

Author: ingfraga

bits/95_api.js

@@ -42,8 +42,8 @@ utils.book_new = function()/*:Workbook*/ {
 
 /* add a worksheet to the end of a given workbook */
 utils.book_append_sheet = function(wb/*:Workbook*/, ws/*:Worksheet*/, name/*:?string*/) {
-	if(!name) for(var i = 1; i <= 0xFFFF; ++i) if(wb.SheetNames.indexOf(name = "Sheet" + i) == -1) break;
-	if(!name) throw new Error("Too many worksheets");
+	if(!name) for(var i = 1; i <= 0xFFFF; ++i, name = undefined) if(wb.SheetNames.indexOf(name = "Sheet" + i) == -1) break;
+	if(!name || wb.SheetNames.length >= 0xFFFF) throw new Error("Too many worksheets");
 	check_ws_name(name);
 	if(wb.SheetNames.indexOf(name) >= 0) throw new Error("Worksheet with name |" + name + "| already exists!");