Fix issue #637 with cash accounts.

app/Http/Controllers/Transaction/ConvertController.php

@@ -182,6 +182,12 @@ class ConvertController extends Controller
                 break;
             case TransactionType::DEPOSIT . '-' . TransactionType::WITHDRAWAL: // three
             case TransactionType::TRANSFER . '-' . TransactionType::WITHDRAWAL: // five
+                if ($data['destination_account_expense'] === '') {
+                    // destination is a cash account.
+                    $destination = $accountRepository->getCashAccount();
+
+                    return $destination;
+                }
                 $data        = [
                     'name'           => $data['destination_account_expense'],
                     'accountType'    => 'expense',
@@ -221,6 +227,14 @@ class ConvertController extends Controller
                 throw new FireflyException('Cannot handle ' . $joined); // @codeCoverageIgnore
             case TransactionType::WITHDRAWAL . '-' . TransactionType::DEPOSIT: // one
             case TransactionType::TRANSFER . '-' . TransactionType::DEPOSIT: // six
+
+                if ($data['source_account_revenue'] === '') {
+                    // destination is a cash account.
+                    $destination = $accountRepository->getCashAccount();
+
+                    return $destination;
+                }
+
                 $data   = [
                     'name'           => $data['source_account_revenue'],
                     'accountType'    => 'revenue',

app/Repositories/Account/AccountRepository.php

@@ -250,6 +250,19 @@ class AccountRepository implements AccountRepositoryInterface
         return $result;
     }
 
+    /**
+     * @return Account
+     */
+    public function getCashAccount(): Account
+    {
+        $type    = AccountType::where('type', AccountType::CASH)->first();
+        $account = Account::firstOrCreateEncrypted(
+            ['user_id' => $this->user->id, 'account_type_id' => $type->id, 'name' => 'Cash account', 'active' => 1]
+        );
+
+        return $account;
+    }
+
     /**
      * Returns the date of the very last transaction in this account.
      *

app/Repositories/Account/AccountRepositoryInterface.php

@@ -36,6 +36,11 @@ interface AccountRepositoryInterface
      */
     public function count(array $types): int;
 
+    /**
+     * @return Account
+     */
+    public function getCashAccount(): Account;
+
     /**
      * Moved here from account CRUD.
      *