fix(migrate): skip bill type backfill when schema is missing

Author: Rocket-Quack

time_tracking/patches/post_model_sync/set_default_bill_type_on_time_bookings.py

@@ -2,10 +2,28 @@
 
 
 def execute():
+	if not _has_bill_type_column():
+		return
+
 	frappe.db.sql(
 		"""
 		update `tabTime Booking`
 		set bill_type = 'Billable'
 		where ifnull(bill_type, '') = ''
 		"""
 	)
+
+
+def _has_bill_type_column():
+	return bool(
+		frappe.db.sql(
+			"""
+			select 1
+			from information_schema.columns
+			where table_schema = database()
+				and table_name = 'tabTime Booking'
+				and column_name = 'bill_type'
+			limit 1
+			"""
+		)
+	)