Fix hot reload under Windows + admin center

Using
9.10 date-based from dec 19
windows 10
jsf ui
nuxeo drive
browser extension
firefox 57

• Follow steps provided in studio jsf tests set 2 from document template to user action
• Hot reload using admin center twice

=> Hot reload crashes with the stack attached

notes:

• server.log contains the actual stack
• stack.txt and context.txt is the error as reflected in the ui, probably just a consequence