Malformed anchor hrefs can cause an app crash

[Jaifroid]

As reported in this comment (but note the article was "Cancer Immunotherapy" in the September 2018 WikiMed, and it has been corrected in later versions), a malformed anchor href causes the app to crash, at least in Edge. The problem was a malformed DOI: reference. Although transient, as a Wikipedia bot no doubt corrected it, our app should be a bit more tolerant of the possibility that this.href, this.protocol and this.host could be undefined. The crash occurs here, and when that is corrected, it occurs here.

A workaround is to use jQuery for those specific this references, as elsewhere in this function. However, we could also or instead add a test, like if (!this.href) return;

[mossroy]

I vote to fix this issue, as the fix you proposed was generic.
If the if(!this.href) test is enough, it might be a less risky modification of the code, except if you see other benefits from switching to jQuery here?

[Jaifroid]

I've created https://github.com/kiwix/kiwix-js/tree/Prevent-app-crash-with-malformed-anchor-hrefs to test the issue. It's got the jQuery fix added to it so I don't forget that fix, but I'll look into the simpler fix.

[Jaifroid]

Just for info, I've re-downloaded the September WikiMed (which I had accidentally deleted), and the problematic article is indeed Immunotherapy, as I had originally stated. It "reliably" causes an app crash on master.