Null-check model choice after :CopilotChatModel

If you dont select anything and just ESC it sets the model to nil atm.

Signed-off-by: Tomas Slusny <[email protected]>

lua/CopilotChat/init.lua

@@ -356,7 +356,9 @@ function M.select_model()
  vim.ui.select(models, {
  prompt = 'Select a model',
  }, function(choice)
- M.config.model = choice
+ if choice then
+ M.config.model = choice
+ end
  end)
  end)
  end)