I have the following line of code:

switchEditors.switchto(ctmce[0]);

which gives this error:

Uncaught TypeError: switchEditors.switchto is not a function

Searching around I found out that, due to changes to the core in WordPress 4.3, switchEditors.switchto() is not available/usable now.

Unfortunately the theme containing the line of code is not update anymore, so I have to correct it manually.

Do you know how can I fix it?

You can see the complete code here.