fix(test): Use single quotes for empty string (constant) (#6871)

* Use single quotes for empty string
since value inside double quotes is considered as Identifier in postgres

* Do not show change log modal when in test

* Revert "Do not show change log modal when in test"

This reverts commit 6c2c3fd80cad3ff491b7d3b60a2b756ba6823bf8.

* Do not show change log modal when in test

- To check it is test environment we are checking if Cypress is
loaded on window object

frappe/model/db_query.py

@@ -458,7 +458,7 @@ class DatabaseQuery(object):
 					f.operator = '='
 
 				value = ""
-				fallback = '""'
+				fallback = "''"
 				can_be_null = True
 
 				if 'ifnull' not in column_name:

frappe/public/js/frappe/desk.js

@@ -72,7 +72,7 @@ frappe.Application = Class.extend({
 			frappe.msgprint(frappe.boot.messages);
 		}
 
-		if (frappe.boot.change_log && frappe.boot.change_log.length) {
+		if (frappe.boot.change_log && frappe.boot.change_log.length && !window.Cypress) {
 			this.show_change_log();
 		} else {
 			this.show_notes();