failcheck

src/main.lua

@@ -647,6 +647,9 @@ local function VP_createstack(buf, dimensions)
 end
 local function VP_splitstack(_stack, x)
     local stack = _stack["stacks"]
+    if #stack == 0 then
+        error("Internal error, splitstack received 0 stacks. There is nothing to split.")
+    end
     local dimensions = _stack["dimensions"]
     local sx = dimensions["sx"]
     local sz = dimensions["sz"]