lost my project too.
Happened after i deleted some songs. Then the preview stopped working, The page openned but just showed the html black background + construct border.
i went to event sheet and found the the audio events were still there, i deleted and tried preview again (without success), I asked to save for then it showed me this error (has action,event action cpp) ( i pressed retry).
Then, i restarted construct when i opened the project showed me the 2nd error, now the project is broken.
my lucky is that i always do backups (and that was easy to recover by chaging event sheet xml).