fix(mason): add nil check to on_stderr callback in install-pylsp-plugins

Author: charliie-dev

lua/modules/configs/completion/mason.lua

@@ -83,7 +83,9 @@ M.setup = function()
 						)
 					end,
 					on_stderr = function(_, msg_stream)
-						vim.notify(msg_stream, vim.log.levels.ERROR, { title = "[lsp] Install Failure" })
+						if msg_stream then
+							vim.notify(msg_stream, vim.log.levels.ERROR, { title = "[lsp] Install Failure" })
+						end
 					end,
 				})
 				:start()