fix(store): init _customProperties for devtools

[rudyxu1102]

Fix #1693

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[posva]

Thanks, there are other places where _customProperties are used that should also execute when adding devtools to prod

[posva]

There is also L671. Can you make sure that part runs with devtools as well?

[codecov-commenter]

Codecov Report

Merging #1704 (8dd8893) into v2 (9864beb) will decrease coverage by 0.72%.
The diff coverage is 44.44%.

@@            Coverage Diff             @@
##               v2    #1704      +/-   ##
==========================================
- Coverage   96.89%   96.16%   -0.73%     
==========================================
  Files          12       12              
  Lines        3159     3158       -1     
  Branches      229      227       -2     
==========================================
- Hits         3061     3037      -24     
- Misses         95      118      +23     
  Partials        3        3              

Impacted Files	Coverage Δ
packages/pinia/src/store.ts	89.91% <44.44%> (-2.43%)	⬇️

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[posva]

Thanks!