Query->count() raises an error if webservice->execute() returns false

[alaxos]

The Query->count() contains the following line:

return $this->__resultSet->total();

But the Query->_execute() method assigns directly the result of the webservice request to $this->__resultSet without checking the returned type:

return $this->__resultSet = $this->_webservice->execute($this);

and according to the doc, the WebserviceInterface->execute() function may return a ResultSet, but also an integer or a boolean:

@return \Muffin\Webservice\ResultSet|int|bool

Therefore for example if the webservice request fails and returns false, $this->__resultSet does not have any total() method and an error is raised.

A solution could be :

if(method_exists($this->__resultSet, 'total')) {
    return $this->__resultSet->total();
} else {
    return false;
}

or

if(is_a($this->__resultSet, '\Cake\Datasource\ResultSetInterface')) {
    return $this->__resultSet->total();
} else {
    return false;
}

[ADmad]

Checking that resultset is instance of \Cake\Datasource\ResultSetInterface sounds good. Would you like to make a PR for it?