share-this.html gives page build error with numeric page titles

[veromary]

Last week I went to update my page for the first time in about a year and had a page build error.
After some hours I found the answer. I had some pages with numeric titles, which used to work fine in 2016, but now numeric titles cause a page build error when pages include _include/share-this.html

The rest seems fine, it even builds fine on my own computer with bundler, just on github.com it gives page build with no specific error message.

Maybe someone knows a way to convert a numeric title to a string to save anyone else the hassle - or at least if someone comes across it might save them time.

Thanks for the great theme too - the more I look into it the more I learn.