Write NaN values to cache when data is missing

[jenshnielsen]

No description provided.

[astafan8]

newsfragment?

[codecov]

Codecov Report

❌ Patch coverage is 88.23529% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.73%. Comparing base (cf9a721) to head (98a07cc).
⚠️ Report is 21 commits behind head on main.

Files with missing lines	Patch %	Lines
src/qcodes/dataset/data_set_cache.py	88.23%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7502   +/-   ##
=======================================
  Coverage   59.72%   59.73%           
=======================================
  Files         347      347           
  Lines       31229    31242   +13     
=======================================
+ Hits        18652    18661    +9     
- Misses      12577    12581    +4     

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