set != NULL

### Problem

Running this command in verbose:

beet -v fingerprint .

Runs fine for a while, then slows and stops, showing this:

```
chroma: /u/mp3/Julie London/Julie Is Her Name, Vol. 1/05 Can't Help Lovin' That Man.m4a: writing fingerprint
Sending event: write
Sending event: after_write
Sending event: database_change
chroma: /u/mp3/Julie London/Julie Is Her Name, Vol. 1/06 I Love You.m4a: fingerprinting

(python3.13:4131682): GStreamer-CRITICAL **: 14:23:13.938: gst_poll_get_read_gpollfd: assertion 'set != NULL' failed
```

### Setup

* OS
Gentoo stable

* Python version:

: backup ~ # python -V
Python 3.13.14
*
* beets version:

backup ~ # beet --version
beets version 2.3.1
Python version 3.13.14
plugins: badfiles, chroma, duplicates, mbsync, missing

* Turning off plugins made problem go away (yes/no):

No

My configuration (output of `beet config`) is:

```yaml
backup /u/mp3 # beet config
directory: /u/mp3
# --------------- Main ---------------

library: /u/mp3/data/musiclibrary.db

# --------------- Plugins ---------------

plugins: [chroma]
chroma:
auto: yes

import:
copy: no
write: yes
move: no
languages: en
quiet: no
```

Start by reproducing `beet -v fingerprint .` with the provided Python 3.13.14, beets 2.3.1, and chroma configuration, then compare behavior with the plugin disabled. Investigate the GStreamer assertion during fingerprinting and determine what change prevents processing from slowing or stopping; done means the command completes without this critical error.

Written by the indexing model from the issue text.