Fix jsFS callback-related crashes#1118

Merged

nevkontakte merged 3 commits intogopherjs:masterfrom

samhocevar-forks:fix/jsfs-callback-arg-count

May 16, 2022

Commits on May 11, 2022

Fix a crash occurring when a jsFS callback is called without arguments
samhocevar
committed
Protect against jsFS callback error argument being undefined
samhocevar
committed

Commits on May 15, 2022

Add a comment to explain fsCall() safety checks
samhocevar
committed