Fail to compile when trying to generate Qtr dtor with an incomplete type

[andrsd]

This helps to find "hidden" memory leaks, when the code happily compiles, but an incorrect code is generated for the dtor causing memory not being freed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.50%. Comparing base (b77d2e9) to head (eba9dc8).
⚠️ Report is 2 commits behind head on 0.12.x.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           0.12.x     #998   +/-   ##
=======================================
  Coverage   76.50%   76.50%           
=======================================
  Files         155      155           
  Lines       10467    10467           
=======================================
  Hits         8008     8008           
  Misses       2459     2459           

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