Fixes a fatal error in the webhook controller when an invalid project…

[ptejada]

Contribution Type: bug fix Link to Bug: N/A

This pull request affects the following areas:

• [ ] Front-End
• [ ] Builder
• [ ] Build Plugins

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• [ ] I have created or updated the relevant documentation for this change on the PHPCI Wiki.
• [x] Do the PHPCI tests pass?

Detailed description of change:

Fixes a fatal error in the webhook controller when an invalid project id is given in the URL