fix(query): set error to null when going to loading state

[TkDodo]

to be aligned with the types, as loading cannot have an error set.

closes #3090

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Sandbox	Source
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[codecov]

Codecov Report

Merging #3106 (bf826a8) into master (2054f5b) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #3106   +/-   ##
=======================================
  Coverage   96.47%   96.47%           
=======================================
  Files          45       45           
  Lines        2270     2270           
  Branches      639      639           
=======================================
  Hits         2190     2190           
  Misses         77       77           
  Partials        3        3           

Impacted Files	Coverage Δ
src/core/query.ts	100.00% <100.00%> (ø)

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[tannerlinsley]

🎉 This PR is included in version 3.34.5 🎉

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[tannerlinsley]

🎉 This PR is included in version 4.0.0-alpha.6 🎉

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