undefined index in libraries_load()

580 $library = cache_get($name, 'cache_libraries');
581 if ($library) {
582 $library = $library->data;
583 }
584 else {
585 $library = libraries_detect($name);
586 cache_set($name, $library, 'cache_libraries');
587 }

I fail to see what is wrong with that code and also how $library['installed'] can not be set (it gets set unconditionally in libraries_detect()).

BTW: Why is libraries.module in your custom folder?

Marking "maintainer needs more info", but the next time I stumble on this, I will mark it "cannot reproduce". I am pretty sure this is an error on your side.

...

I also am getting this. In my case it is because there is no version number for the library. In hook_libraries_info the 'version arguments' is not optional, but there doesn't seem to be any way to cope with a library that doesn't have a version number embedded in one of it's files.

but there doesn't seem to be any way to cope with a library that doesn't have a version number embedded in one of it's files

What library is that? That seems to be an edge-case.

What you can do to solve this is simply set $library['version'] in hook_libraries_info(). The version detection will not run in that case.

Thanks, I worked out I could just create my own version callback and set it there. Everything is working for me now.

Great, marking fixed.
There was no response regarding the initial report, so that should be fine.