Fix opening bmlab files with multiple repetitions

[raimund-schluessler]

Because I am obviously stupid 🙈🙃, the implementation of #22 had an issue with opening bmlab files with multiple repetitions. This fixes it.
We should add a bmlab test file for checking this, but I don't have a small enough file at hand at the moment.
@juko1 This fixes BrillouinMicroscopy/BMicro#150.

[codecov-commenter]

Codecov Report

Merging #26 (5b46c31) into main (17102d8) will increase coverage by 0.59%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #26      +/-   ##
==========================================
+ Coverage   77.64%   78.24%   +0.59%     
==========================================
  Files          35       35              
  Lines        2425     2482      +57     
==========================================
+ Hits         1883     1942      +59     
+ Misses        542      540       -2     

Impacted Files	Coverage Δ
impose/formats/fmt_bm_bmlab.py	100.00% <100.00%> (+3.77%)	⬆️
impose/gui/visualize.py	93.37% <0.00%> (-0.15%)	⬇️
impose/flblend.py	99.39% <0.00%> (+1.07%)	⬆️

📣 Codecov can now indicate which changes are the most critical in Pull Requests. Learn more

[paulmueller]

I would be happy to merge this if you added the test file. Up to 1MB is still fine I think.

[raimund-schluessler]

I would be happy to merge this if you added the test file. Up to 1MB is still fine I think.

Done. The test successfully fails without the fix in 360b371 🙂

[paulmueller]

Thanks for sticking to the new test data naming scheme.