fix: ignore empty customer/supplier in item query (#29610)

* fix: dont try to filter by customer/supplier if None

* test: item query with emtpy supplier
diff --git a/erpnext/controllers/tests/test_queries.py b/erpnext/controllers/tests/test_queries.py
index 908d78c..60d1733 100644
--- a/erpnext/controllers/tests/test_queries.py
+++ b/erpnext/controllers/tests/test_queries.py
@@ -56,6 +56,12 @@
 		bundled_stock_items = query(txt="_test product bundle item 5", filters={"is_stock_item": 1})
 		self.assertEqual(len(bundled_stock_items), 0)
 
+		# empty customer/supplier should be stripped of instead of failure
+		query(txt="", filters={"customer": None})
+		query(txt="", filters={"customer": ""})
+		query(txt="", filters={"supplier": None})
+		query(txt="", filters={"supplier": ""})
+
 	def test_bom_qury(self):
 		query = add_default_params(queries.bom, "BOM")