XLSX !protect check on write [ci skip]

Author: hu0p

bits/67_wsxml.js

@@ -577,7 +577,7 @@ function write_ws_xml(idx/*:number*/, opts, wb/*:Workbook*/, rels)/*:string*/ {
 
 	/* sheetCalcPr */
 
-	if(ws['!protect'] != null) o[o.length] = write_ws_xml_protection(ws['!protect']);
+	if(ws['!protect']) o[o.length] = write_ws_xml_protection(ws['!protect']);
 
 	/* protectedRanges */
 	/* scenarios */