Fix/script without icon

[mstv]

Proposed changes

• It is allowed to not assign an icon to a user script.
  So avoid regarding exceptions.
• Display the shortcuts assigned to the user scripts.
• Fixup the condition for showing the user scripts arguments cheat sheet again after closing it.

Before

NBug exceptions unless icons are defined

After

Test methodology

• manual

Test environment(s)

• Git Extensions 3.3.0
• Build 3486ba0
• Git 2.26.0.windows.1
• Microsoft Windows NT 6.2.9200.0
• .NET Framework 4.8.4180.0
• DPI 96dpi (no scaling)

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✒️ I contribute this code under The Developer Certificate of Origin.

[mstv]

Should be integrated into 3.4, too. Will we merge the master into release/3.4?
Only the version number must be reverted on merge.

[codecov]

Codecov Report

Merging #8111 into master will increase coverage by 0.00%.
The diff coverage is 12.50%.

@@           Coverage Diff           @@
##           master    #8111   +/-   ##
=======================================
  Coverage   49.54%   49.55%           
=======================================
  Files         847      847           
  Lines       60916    60921    +5     
  Branches    10924    10932    +8     
=======================================
+ Hits        30182    30187    +5     
- Misses      28497    28502    +5     
+ Partials     2237     2232    -5     

Flag	Coverage Δ
#production	37.37% <12.50%> (+<0.01%)	⬆️
#tests	94.85% <ø> (-0.01%)	⬇️

[RussKie]

Merge at will. Please port to 3.4 as well.

[RussKie]

We should avoid merging fixup commits.

[mstv]

We should avoid merging fixup commits.

Maybe I chose the wrong wording: These commits fix up / resolve issues. They are no "fixup!" to previous commits.