use null instead of undefined

web/src/components/TransactionInputRow.vue

@@ -16,9 +16,9 @@ const TX = ref<Transaction>({
     Memo: "",
     Amount: 0,
     Payee: "",
-    PayeeID: undefined,
+    PayeeID: null,
     Category: "",
-    CategoryID: undefined,
+    CategoryID: null,
     CategoryGroup: "",
     GroupID: "",
     ID: "",

web/src/stores/transactions.ts

@@ -17,12 +17,12 @@ export interface Transaction {
     TransferAccount: string;
     CategoryGroup: string;
     Category: string;
-    CategoryID: string | undefined;
+    CategoryID: string | null;
     Memo: string;
     Status: string;
     GroupID: string;
     Payee: string;
-    PayeeID: string | undefined;
+    PayeeID: string | null;
     Amount: number;
     Reconciled: boolean;
     Account: string;