hotfix: missing check key for member balance

app/views/members/show.html.erb

 <h1><%= t(:member_card) %></h1>
 <br />
 <h2>Balance</h2>
-<%if InvoicingLedgerItem.account_summary(@member.id).empty?%>
+<%if InvoicingLedgerItem.account_summary(@member.id).has_key? :EUR%>
 <%= number_to_currency(0) %>
 <%else%>
 <%= number_to_currency(InvoicingLedgerItem.account_summary(@member.id)[:EUR].balance) %>