bug#58706: 29.0.50; [noverlay] `get-pos-property' misses overlay start

[Matt Armstrong]

X-Debbugs-CC: Stefan Monnier <monnier@iro.umontreal.ca>

The following test passes on mainline but doesn't on feature/noverlay.
On the noverlay branch `get-pos-property' returns nil.

(ert-deftest test-get-pos-property-overlay-beg ()
  "Test `get-pos-property' at the beginning of an overlay."
  (with-temp-buffer
    (insert (make-string 10 ?x))
    (let ((overlay (make-overlay 5 7)))
      (overlay-put overlay 'forty-two 42))
    (should (equal 42 (get-pos-property 5 'forty-two)))))