Having your head inside a glass block now makes the world black, like in opaque blocks. Previously it just turned the glass invisible, just like it still does in Spectator mode. Switching to third person view also restores the ability to see the world, but the camera does not move out of the glass block.
Probably for the same reason, glass blocks now suffocate players and mobs with their head inside of it, breaking lots of contraptions.
Related issues
is duplicated by
MC-142352
Glass suffocates and is opaque when player's head is in it.
MC-142815
Glass Blocks Suffocate Entities
MC-143478
Can no longer see while your head is in a (stained) glass block
MC-143812
Glass acts like solid blocks sometimes
MC-146290
When stuck/suffocating in a glass block the camera goes black, just like when stuck in an opaque black
relates to
Comments
FaRo1
Asteraoth
Glass blocks are now solid, see https://twitter.com/jeb_/status/1108312583596068864. The duplicates mention your issue (MC-143478, MC-143812, MC-142352 and MC-142815).
FaRo1
I would recommend closing the first two as duplicates of this one instead. The others are correctly closed, because they are about suffocation.
Asteraoth
Linked those reports to this issue.
muzikbike
This has also affected ice for far longer. MC-73784
The other report doesn't mention that you can't see anything from within glass, which is surely not intended, because glass is transparent.