If a parameter name is modified in the TemplateData editor, then immediately reverted back to its original value, the TemplateData editor crash when clicking on "Done" :
- the TemplateData editor content is blank and buttons do not do anything, even "cancel" : it's impossible to go back to the page editor
- the modification of the templatedata is lost
- other modification to the template (or it's doc subpage) can be kept on Firefox by reloading the page but are also lost on Edge or Chrome.
Step to reproduce :
- Edit a template with parameters (eg w:Template:Template sandbox)
- Click on "Manage TemplateData"
- If necessary click on "Add 3 suggested parameters" (but the bug is also present on existing params)
- click on a parameter (named or not)
- change the name (eg. add a caracter)
- restore the initial name (by Ctrl+z, paste or manually)
- click "Done"
Tested on fr.wikipedia and en.wikipedia and test.wikipedia.org on 28/7/2016, connected or not, with Firefox Chrome and Edge, Windows 10 and Ubuntu, all failed.