Fix some addUPI telemetry issues

[aptiko]

Checklist:

• [ ] All tests are passing
• [ ] I have added any necessary documentation and/or release notes
• [ ] I have followed the commit message guidelines and the "before submitting a pull request" guidelines
• [ ] If I introduced (or abolished) any third-party library, I will write a short paragraph in this PR according to the guidelines
• [ ] I have removed all obsoleted code

[codecov[bot]]

Codecov Report

Merging #504 (7fab6c8) into master (92d0a54) will decrease coverage by 0.04%. The diff coverage is 92.30%.

@@            Coverage Diff             @@
##           master     #504      +/-   ##
==========================================
- Coverage   98.21%   98.18%   -0.04%     
==========================================
  Files          41       41              
  Lines        2134     2144      +10     
==========================================
+ Hits         2096     2105       +9     
- Misses         38       39       +1     

Files Changed	Coverage Δ
enhydris/telemetry/types/addupi.py	98.73% <85.71%> (-1.27%)	:arrow_down:
enhydris/telemetry/forms.py	100.00% <100.00%> (ø)

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