fix: failures of preview-link in Node.js runtime

[PierrickVoulet]

• Only send one response in all cases.
• Filter card click events before matched URLs to avoid unreachable code.

[vinay-google]

Instead of having the return statement on its own line, we can just do it wherever we are either doing res.send or res.json. For example:

return res.send('Hello! This function is meant to be used in a Google Chat Space.');

[PierrickVoulet]

Instead of having the return statement on its own line, we can just do it wherever we are either doing res.send or res.json. For example:

return res.send('Hello! This function is meant to be used in a Google Chat Space.');

Agreed and done! I also added returns even for latest statements for consistency and best practice.