Fix to workaround #13 when a node seems undefined

init.lua

@@ -90,6 +90,12 @@ function rspawn:newspawn(pos, radius)
         under = minetest.registered_nodes[under]
         over = minetest.registered_nodes[over]
 
+        if under == nil or over == nil then
+            -- `under` or `over` could be nil if a mod that defined that node was removed.
+            -- Not something this mod can resolve, and so we just ignore it.
+            rspawn:debug("Found an undefined node around "..minetest.pos_to_string(anode))
+
+        else
             if under.walkable
              and not over.walkable
              and not minetest.is_protected(anode, "")
@@ -102,6 +108,7 @@ function rspawn:newspawn(pos, radius)
                 end
             end
         end
+    end
 
     if #validnodes > 0 then
         rspawn:debug("Valid spawn points found with radius "..tostring(radius))