Mining terracotta with a Smelter's Pickaxe always returns White Glazed Terracotta

[NicksWorld]

Description (Required)

Whenever a "Smelter's Pickaxe" is used to mine any type of terracotta regardless of color, it always drops a white glazed terracotta instead of a glazed terracotta of the respective color.
Example: You mine green terracotta with a Smelter's Pickaxe.
Expected result: You obtain a green glazed terracotta, such as its smelting recipe.
Result: You obtain a single white glazed terracotta.

Server Log

The server log is at https://pastebin.com/F1Gr2emi and doesn't appear to contain any relevant errors, but one did appear saying that it couldn't convert " " to a number.

Evidence / Proof (Required)

Mining the terracotta (Waila showing block type), and the white glazed terracotta being dropped
https://i.gyazo.com/8e19043602219a64696b0fb8e07ede35.gif

Environment (Required)

CraftBukkit v1_12_R1

CS-CoreLib vv1.5.18
Slimefun vDEV (Slimefun4 - #52 as listed on repo server)
Installed addons (0)

Note: there are no other plugins on the server