fix: Only validate fetch from when user modifies it

(cherry picked from commit b044ffe)

frappe/core/doctype/doctype/doctype.py

@@ -1590,6 +1590,9 @@ def check_no_of_ratings(docfield):
 				frappe.throw(_("Options for Rating field can range from 3 to 10"))
 
 	def check_fetch_from(docfield):
+		if not frappe.request:
+			return
+
 		fetch_from = docfield.fetch_from
 		fieldname = docfield.fieldname
 		if not fetch_from: