Don't crash if the member doesn't exist

Check for member existance before accesing internal values of the
member.

src/transaction/TransactionList.js

@@ -41,15 +41,18 @@ function TransactionList() {
     setTypes(newTypes);
   };
 
+  let memberStr = "";
+  if (transaction.member) {
+    memberStr = transaction.member.name + " (" + transaction.member.num + ")";
+  }
+
   const entries = transactions.map((transaction) => {
     return (
       <TransactionTr key={transaction.ID} transaction={transaction}>
         <td>{icon(transaction)}</td>
         <td>{printTransactionID(transaction)}</td>
         <td>{printDate(transaction.date)}</td>
-        <td>
-          {transaction.member.name} ({transaction.member.num})
-        </td>
+        <td>{memberStr}</td>
         <td>{transaction.proxy ? transaction.proxy.name : ""}</td>
         <td>{printMoney(transaction.total) + " €"}</td>
       </TransactionTr>