Improve DataField::$value type

[vjik]

Q	A
Is bugfix?	❌
New feature?	❌
Breaks BC?	✔️

[codecov]

Codecov Report

Attention: Patch coverage is 89.47368% with 2 lines in your changes missing coverage. Please review.

Project coverage is 82.81%. Comparing base (5a09ab1) to head (e1d2be9).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/DetailView.php	89.47%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #259      +/-   ##
============================================
- Coverage     82.89%   82.81%   -0.08%     
+ Complexity      624      621       -3     
============================================
  Files            51       51              
  Lines          2110     2112       +2     
============================================
  Hits           1749     1749              
- Misses          361      363       +2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.