Fix dev mode error from LGV overview scalebar

[cmdcolin]

error message, observed only in chrome devmode in lgv header

Cannot update a component (Unknown) while rendering a different component (Unknown)

spotted by @garrettjstevens

the fix is to avoid calling actions on the dynamically created MST object during render time

[codecov]

Codecov Report

Merging #3937 (c0655ec) into main (eaa4ffa) will decrease coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #3937      +/-   ##
==========================================
- Coverage   63.90%   63.88%   -0.02%     
==========================================
  Files        1013     1013              
  Lines       30165    30166       +1     
  Branches     7194     7194              
==========================================
- Hits        19276    19271       -5     
- Misses      10726    10734       +8     
+ Partials      163      161       -2     

Files Changed	Coverage Δ
...c/LinearGenomeView/components/OverviewScalebar.tsx	86.31% <100.00%> (+0.14%)	⬆️

... and 5 files with indirect coverage changes

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[cmdcolin]

note: the unknown unknown thing is probably best fixed by adding names to the anonymous functions passed to observer