fw_node: release allocated GError in event loop
fw_node: release allocated GError in event loop

In event loop, error is not reported to users directly. Once GError is
allocated, it should be released, but not.

This commit fixes the bug.

Fixes: c8a0a9651afc ("fw_node: add an API to create GSource to listen events for node on IEEE 1394 bus")
Signed-off-by: Takashi Sakamoto <d5ec7d0cd8074757a1f5eb708bc105c3065a65ea@sakamocchi.jp>

takaswie/libhinawa,takaswie/libhinawa