Hotfix for issue with stories panel

[Hypnosphi]

Issue: once you hide the stories ("left") panel, you can't open it again. In fact, it doesn't even hide:

Related: #1614

Unfortunately, I overlooked those lines when reviewing #1598. Unfortunately, I can't figure out where this error get caught so that the failure is silent.

@igor-dv, I think it's better to use an additional state field instead of input ref there

[codecov]

Codecov Report

Merging #1689 into master will increase coverage by 0.01%.
The diff coverage is 33.33%.

@@            Coverage Diff             @@
##           master    #1689      +/-   ##
==========================================
+ Coverage   20.87%   20.88%   +0.01%     
==========================================
  Files         251      251              
  Lines        5629     5631       +2     
  Branches      676      669       -7     
==========================================
+ Hits         1175     1176       +1     
- Misses       3933     3964      +31     
+ Partials      521      491      -30

Impacted Files	Coverage Δ
...rc/modules/ui/components/left_panel/text_filter.js	34.66% <33.33%> (+0.42%)	⬆️
app/vue/src/server/config/babel.js	0% <0%> (-100%)	⬇️
app/vue/src/server/babel_config.js	0% <0%> (-83.88%)	⬇️
addons/storyshots/src/storybook-channel-mock.js	0% <0%> (ø)	⬆️
lib/ui/src/modules/ui/containers/layout.js	12.5% <0%> (ø)	⬆️
lib/ui/src/modules/ui/containers/down_panel.js	23.52% <0%> (ø)	⬆️
.../ui/src/modules/ui/components/layout/dimensions.js	15.62% <0%> (ø)	⬆️
addons/storyshots/src/require_context.js	0% <0%> (ø)	⬆️
addons/knobs/src/components/PropForm.js	8.51% <0%> (ø)	⬆️
addons/knobs/src/components/types/Color.js	8% <0%> (ø)	⬆️
... and 24 more

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[igor-dv]

Oh, my fault.