fix: error due to passing None in scrub
diff --git a/erpnext/accounts/report/gross_profit/gross_profit.py b/erpnext/accounts/report/gross_profit/gross_profit.py
index 56bd7c2..7ecc695 100644
--- a/erpnext/accounts/report/gross_profit/gross_profit.py
+++ b/erpnext/accounts/report/gross_profit/gross_profit.py
@@ -200,7 +200,7 @@
 
 	def skip_row(self, row, product_bundles):
 		if self.filters.get("group_by") != "Invoice":
-			if not row.get(scrub(self.filters.get("group_by"))):
+			if not row.get(scrub(self.filters.get("group_by", ""))):
 				return True
 		elif row.get("is_return") == 1:
 			return True