Emergency stop: job aborted, no legal end found

Emergency stop.

<*> Main_file.tex
                 
*** (job aborted, no legal end found)

 
Here is how much of TeX's memory you used:
 13088 strings out of 492164
 254952 string characters out of 6125314
 329325 words of memory out of 5000000
 17107 multiletter control sequences out of 15000+600000
 12006 words of font info for 44 fonts, out of 8000000 for 9000
 1141 hyphenation exceptions out of 8191
 60i,12n,54p,634b,492s stack positions out of 5000i,500n,10000p,200000b,80000s
!  ==> Fatal error occurred, no output PDF file produced!