Fix Progress Bar issue in long-press when releasing

[nroggeman-ledger]

Description

The goal is to fix a potential issue when using long-press button.
If the touch is releasead when the first "step" is drawn, this step is not deleted in the progress bar

Changes include

• Bugfix (non-breaking change that solves an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)
• Tests
• Documentation
• Other (for changes that might not fit in any category)

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 35.67%. Comparing base (766b9c1) to head (f19d087).

Files with missing lines	Patch %	Lines
lib_nbgl/src/nbgl_screen.c	0.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master     #769       +/-   ##
===========================================
- Coverage   60.32%   35.67%   -24.65%     
===========================================
  Files          13       13               
  Lines        1807     1595      -212     
===========================================
- Hits         1090      569      -521     
- Misses        717     1026      +309     

Flag	Coverage Δ
unittests	35.67% <0.00%> (-24.65%)	⬇️

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