[tex2jax] [2.7.4] MathJax no longer processes \({\)

Changes in 2.7.4 for #1960 (closed) cause MathJax to no longer process unbalanced braces like \({\).

This is due to https://github.com/mathjax/MathJax/blob/419b0a6eee7eefc0f85e47f7d4f8227ec28b8e57/unpacked/extensions/tex2jax.js#L171

which should be

        else if (!this.search.start && !this.search.close) rescan = this.search;

This came from this MathJax user's forum post.