DDC-2273: [GH-566] Added missing return statement to AbstractCommand.

[doctrinebot]

Jira issue originally created by user @beberlei:

This issue is created automatically through a Github pull request on behalf of BenMorel:

Url: #566

Message:

The AbstractCommand::execute() method should return an integer, or null.

Although in PHP, omitting the return statement is equivalent to returning null, it is recommended to put an explicit return to clearly differentiate it from return void.

I've added return 0; here, keeping the existent behavior.

[doctrinebot]

Comment created by @beberlei:

A related Github Pull-Request [GH-566] was closed
#566

[doctrinebot]

Comment created by @FabioBatSilva:

Merged : d3cbdfc

[doctrinebot]

Issue was closed with resolution "Fixed"

[doctrinebot]

Comment created by @doctrinebot:

A related Github Pull-Request [GH-566] was closed:
doctrine/dbal#566