Allow running polybar without BAR argument

[dvermd]

The configuration file must declare a single bar to be able to not name
it.

What type of PR is this? (check all applicable)

• Refactor
• Feature
• Bug Fix
• Optimization
• Documentation Update
• Other: Replace this with a description of the type of this PR

Description

This PR allows to run polybar without BAR argument if the configuration only defines one bar.

Related Issues & Documents

Closes #2525

Documentation (check all applicable)

• This PR requires changes to the Wiki documentation. The Home page must be updated
• This PR requires changes to the documentation inside the git repo (please add them to the PR).
• Does not require documentation changes

[codecov]

Codecov Report

Merging #2526 (de29523) into master (282b0f4) will decrease coverage by 0.01%.
The diff coverage is 4.00%.

@@            Coverage Diff             @@
##           master    #2526      +/-   ##
==========================================
- Coverage   10.47%   10.45%   -0.02%     
==========================================
  Files         147      147              
  Lines       10166    10182      +16     
==========================================
  Hits         1065     1065              
- Misses       9101     9117      +16     

Flag	Coverage Δ
unittests	10.45% <4.00%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
include/components/config.hpp	0.00% <ø> (ø)
include/components/config_parser.hpp	100.00% <ø> (ø)
src/components/config.cpp	0.00% <0.00%> (ø)
src/components/config_parser.cpp	44.72% <0.00%> (-4.94%)	⬇️
src/main.cpp	0.00% <0.00%> (ø)
src/components/command_line.cpp	62.96% <100.00%> (ø)

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[patrick96]

Nice :)

The only blocker is that polybar bar-that-doesnt-exist no longer throws an error.

I also added some suggestion for more user-friendly error messages.

[patrick96]

Perfect! Thanks a lot 😃