Remove nil values from snippets blobs

Working on https://gitlab.com/gitlab-org/gitlab/-/issues/299133, we discovered that there are situations where the blobs retrieved from the snippet repository might have a nil blob among the results and that breaks the VUE code.

> snippet.blobs
=> [nil,
 #<Gitlab::Git::Blob:0x0000555aaa63c090
  @binary=false,
  @commit_id="master",
  @data="zxczxc",
  @id="742b9697a6ce2ec4519cf737c5056baceb2670b6",
  @loaded_all_data=true,
  @loaded_size=6,
  @mode="100644",
  @name="zxczxc",
  @path="zxczxc",
  @size=6>]

We need to ensure that in the Snippet#blobs we don't return any nil value.