fix erroring when object has no parent

Basalt/objects/Container.lua

@@ -110,7 +110,7 @@ return function(name, basalt)
         objId = 0
         evId = 0
         focusedChild = nil
-        parent:removeEvents(self)
+        if parent ~= nil then parent:removeEvents(self) end
     end
 
     local function updateZIndex(self, element, newZ)
@@ -426,4 +426,4 @@ return function(name, basalt)
 
     container.__index = container
     return setmetatable(container, base)
-end
+end