TypeError: Cannot read property 'rowNode' of undefined

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Describe the problem you’re having:
Loading the page the first time:
TypeError: Cannot read property 'rowNode' of undefined at setTimeout (https://my.domain.com/js/FeedTree.js?1548668474:276:28)

If possible include steps to reproduce the problem:
Only happens if loading fresh. Not happening on reload.

tt-rss version (including git commit id):
v18.12 (2777592)

Platform (i.e. Linux distro, PHP, PostgreSQL, etc) veRaspbian, PHP7x 1.10.3
Raspbian Stretch Lite (Nov 2018), PHP 7.0, PostgreSQL 9.6.10, nginx 1.10.3

Please provide any additional information below:

related: K shortcut problem - #8 by lanterne

i’ll take a look later today; should be an easy fix

how about this https://git.tt-rss.org/fox/tt-rss/commit/42e0c7a4202fdd4594fb50afb1aeec77332cae0a + next one

Thanks! The check worked!