SOAP connection problems after 1.9.3.0 update

Same error with another extension here. system.log says

Argument 1 passed to Mage_Api_Model_Server_Handler_Abstract::processingMethodResult() must be of the type array, string given, called in app/code/core/Mage/Api/Model/Server/Handler/Abstract.php...

I think the problem is the new method

Mage_Api_Model_Server_Handler_Abstract::processingMethodResult(array $result)

which only accepts arrays. So every Api function returning a scalar value will throw this error. To get this going again i copied app/code/core/Mage/Api/Model/Server/Handler/Abstract.php to app/code/local/Mage/Api/Model/Server/Handler/Abstract.php and patched processingMethodResult:

public function processingMethodResult($result)
{
    if (is_array($result)) {
        foreach ($result as &$row) {
            if (!is_null($row) && !is_bool($row) && !is_numeric($row)) {
                if (is_array($row)) {
                    $row = $this->processingMethodResult($row);
                } else {
                    $row = $this->processingRow($row);
                }
            }
        }
    } else {
        if (!is_null($result) && !is_bool($result) && !is_numeric($result)) {
            $result = $this->processingRow($result);
        }
    }
    return $result;
}