Avoid errors from breakpoint split view related to getBoundingClientRect on null track

[cmdcolin]

Seen on master while flipping through SV inspector and launching breakpoint split views

[codecov]

Codecov Report

Merging #1559 (b75f025) into master (9b27355) will increase coverage by 0.01%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #1559      +/-   ##
==========================================
+ Coverage   59.50%   59.51%   +0.01%     
==========================================
  Files         435      435              
  Lines       19556    19557       +1     
  Branches     4561     4562       +1     
==========================================
+ Hits        11636    11640       +4     
+ Misses       7626     7623       -3     
  Partials      294      294              

Impacted Files	Coverage Δ
plugins/breakpoint-split-view/src/util.ts	9.52% <0.00%> (-0.48%)	⬇️
packages/core/util/analytics.ts	86.48% <0.00%> (+2.70%)	⬆️
...inearGenomeView/components/RefNameAutocomplete.tsx	89.65% <0.00%> (+3.44%)	⬆️
...r-view/src/BaseChordDisplay/components/Loading.tsx	100.00% <0.00%> (+5.00%)	⬆️

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[cmdcolin]

This is somewhat weird and hard to trigger. Maybe merge this for now and if we see anything weird where squiggles are not drawn properly (e.g. uses the height 0 branch from this) then we can re-examine