fix: validate last_gl_update exists before comparing (#46464)

erpnext/accounts/doctype/account/account.py

@@ -605,6 +605,7 @@ def _ensure_idle_system():
 	if frappe.flags.in_test:
 		return
 
+	last_gl_update = None
 	try:
 		# We also lock inserts to GL entry table with for_update here.
 		last_gl_update = frappe.db.get_value("GL Entry", {}, "modified", for_update=True, wait=False)
@@ -612,6 +613,9 @@ def _ensure_idle_system():
 		# wait=False fails immediately if there's an active transaction.
 		last_gl_update = add_to_date(None, seconds=-1)
 
+	if not last_gl_update:
+		return
+
 	if last_gl_update > add_to_date(None, minutes=-5):
 		frappe.throw(
 			_(