fix: handle invalid URL in YouTube getVideoId()

[0xDaizz]

Summary

• Added try-catch around new URL(this.url) in getVideoId() to prevent TypeError: Invalid URL when this.url is undefined or malformed
• Returns empty string on failure instead of throwing, consistent with the existing || '' fallback

Motivation

When the YouTube extractor receives an undefined or invalid URL, new URL(this.url) throws an unhandled TypeError: Invalid URL (input: 'undefined') to stderr. This happens for certain YouTube videos where the URL isn't properly passed through the extractor pipeline.

Note: PR #51 fixed a related but different issue (youtu.be short URL parsing). This fix addresses the case where this.url itself is undefined/invalid, which still occurs in v0.13.0.

Test plan

• YouTube video with valid URL → works as before
• YouTube extractor with undefined URL → returns empty string, no TypeError