[Minor] Report related fixes (#14620)

* fix in query incase list is empty

* periodicity not found error
when called from consolidated financial statements and custom cash flow is activated

* unset currency filter to apply default currency or so

* python 2 - 3 fix

erpnext/public/js/utils.js

@@ -15,7 +15,8 @@ $.extend(erpnext, {
 
 	get_presentation_currency_list: () => {
 		const docs = frappe.boot.docs;
-		const currency_list = docs.filter(d => d.doctype === ":Currency").map(d => d.name);
+		let currency_list = docs.filter(d => d.doctype === ":Currency").map(d => d.name);
+		currency_list.unshift("");
 		return currency_list;
 	},