Make //clearobjects remove unknown objects (#244)

worldedit/manipulations.lua

@@ -644,7 +644,7 @@ function worldedit.clear_objects(pos1, pos2)
 			return false
 		end
 		local entity = obj:get_luaentity()
-		return not entity or not entity.name:find("^worldedit:")
+		return not (entity and entity.name:find("^worldedit:"))
 	end
 
 	-- Offset positions to include full nodes (positions are in the center of nodes)
@@ -691,4 +691,3 @@ function worldedit.clear_objects(pos1, pos2)
 	end
 	return count
 end
-