Make sure edit of liability always works.

app/Http/Requests/AccountFormRequest.php

@@ -82,7 +82,8 @@ class AccountFormRequest extends FormRequest
             $data['account_type_name'] = null;
             $data['account_type_id']   = $this->convertInteger('liability_type_id');
             if ('' !== $data['opening_balance']) {
-                $data['opening_balance'] = app('steam')->negative($data['opening_balance']);
+                // opening balance is always positive for liabilities
+                $data['opening_balance'] = app('steam')->positive($data['opening_balance']);
             }
         }