slab grapical glitches.

Thank you for your report!
However, this issue has been temporarily closed as Awaiting Response.

We do not have enough information to find the cause of this issue.
Please force a crash by pressing F3 + C for 10 seconds while in-game and attach the crash report ([minecraft/crash-reports/crash-<DATE>-client.txt|http://hopper.minecraft.net/help/guides/finding-minecraft-data-folder]) here.

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This issue duplicates MC-122643.
MC-122643 is more complete.

Forward-resolved to MC-122643