fix: display invalid tags as they are instead of hiding them

[Zaphoood]

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

• Refactor
• Feature
• Bug Fix
• Optimization
• Documentation Update
• Other

Description

If a formatting string contains an invalid/unsupported tag, it is displayed on the bar as-is in order to make the user aware that there's a mistake in their config.
Before, invalid tags would just be hidden.

Related Issues & Documents

Fixes #2713

Documentation (check all applicable)

• This PR requires changes to the Wiki documentation (describe the changes)
• 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 #2714 (0da197f) into master (f0dbb4c) will increase coverage by 0.00%.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##           master    #2714   +/-   ##
=======================================
  Coverage   13.56%   13.57%           
=======================================
  Files         152      152           
  Lines       11357    11354    -3     
=======================================
  Hits         1541     1541           
+ Misses       9816     9813    -3     

Flag	Coverage Δ
unittests	13.57% <0.00%> (+<0.01%)	⬆️

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

Impacted Files	Coverage Δ
include/modules/meta/base.hpp	0.00% <ø> (ø)
include/modules/meta/base.inl	0.00% <0.00%> (ø)
src/modules/bspwm.cpp	0.00% <0.00%> (ø)
src/modules/meta/base.cpp	0.00% <0.00%> (ø)

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[patrick96]

We unfortunately really need to use format->tags to check validity. I wish we could simplify the spacing calculations but it could potentially break a lot of configs.