"Share link" in the menu is disabled on file pages - it does not bring up the sharing dialog when you tap on it - but the menu item appears nevertheless.
Steps:
Go to the MACS J1149 Lensed Star 1 article
Tap on the lead image
Go to the file page for the image
Hit the menu in the upper right
Expected:
Standard "Share sheet" to share link to the file page appears.
Actual:
"Share link" appears in the menu, but when a user taps on it no sharing dialog appears.

