MongoDB DropIndexes() fails when there is no index

[xiaoyi510]

What steps will reproduce the problem?

What's expected?

What do you get instead?

Additional info

Q	A
Yii version	2
Yii MongoDB version	2.1.7
MongoDB server version	4.x
PHP version	7.2
Operating system	LINUX

MongoDB DropIndexes() fails when there is no index

\yii\mongodb\Collection::dropAllIndexes
/**
     * Drops all indexes for this collection.
     * @throws Exception on failure.
     * @return int count of dropped indexes.
     */
    public function dropAllIndexes()
    {
        $result = $this->database->createCommand()->dropIndexes($this->name, '*');
        return $result['nIndexesWas'];
    }

nIndexesWas index does not return this field when deleting a collection without an index

Should be

  public function dropAllIndexes()
    {
        $result = $this->database->createCommand()->dropIndexes($this->name, '*');
        return $result['nIndexesWas']??0;
    }

[samdark]

Looks valid. Do you want to prepare a pull request?