fix: filter out null entries in episode list

[2547techno]

closes #568

The Issue

episodeList can appear in the form:

[null, null, {...}, ...]

This happens when the anilist api does not return the full list of episodes for an anime.

In the case of One Piece (#568), only ep. 1122 is returned from the api, leaving 1121 null's in the list before the first entry with actual episode data, resulting in the following error:

EpisodeList.svelte:14
Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'episode')
    at get_each_context (EpisodeList.svelte:14:65)
    at Object.update [as p] (EpisodeList.svelte:61:7)
    at update (scheduler.js:119:1)
    at flush (scheduler.js:79:1)

due to the destructuring of list entries here:

miru/common/views/ViewAnime/EpisodeList.svelte

Line 61 in 6a8d0cb

{#each episodeOrder ? episodeList : [...episodeList].reverse() as { episode, image, summary, rating, title, length, airdate, filler }}