Torches and lanterns float above walls

^{Update by [Mojang] Mega_Spud (Jay Wells):}
Summary:
Torches and lanterns float above walls, instead of making pillars below for support.

Steps to Reproduce:

1. Place a section of walls, both one block high and two or more blocks high
2. Place torches and lanterns above the walls

Observed Results:
The torches / lanterns placed on the walls do not create support pillars; they float above instead.

Expected Results:
They should create support pillars, just as they did in previous versions.

Screenshots/Videos attached: Yes

Notes:

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Original Description: