Make parse_1d_scan_coords() more robust

[alongd]

The parse_1d_scan_coords() crashed for a specific TS scan output file for two independent reasons. Both bugs were fixed now, and a test was added.

[codecov[bot]]

Codecov Report

Merging #607 (1c2f580) into main (a9bc6ad) will increase coverage by 0.01%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #607      +/-   ##
==========================================
+ Coverage   72.16%   72.17%   +0.01%     
==========================================
  Files          97       97              
  Lines       25551    25559       +8     
  Branches     5388     5390       +2     
==========================================
+ Hits        18438    18448      +10     
+ Misses       5755     5753       -2     
  Partials     1358     1358              

Impacted Files	Coverage Δ
arc/parser.py	84.62% <100.00%> (+0.08%)	:arrow_up:
arc/parser_test.py	100.00% <100.00%> (ø)

... and 2 files with indirect coverage changes

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[alongd]

Thanks @kfir4444, the file size was reduced