Fix undeclared global variable warning at startup

DISABLE_GOLD_SPEAR

defaults.lua

@@ -4,3 +4,4 @@ DISABLE_COPPER_SPEAR = false
 DISABLE_BRONZE_SPEAR = false
 DISABLE_DIAMOND_SPEAR = false
 DISABLE_OBSIDIAN_SPEAR = false
+DISABLE_GOLD_SPEAR = false