Where do nimErr's comes from?

[guibar]

Thas is just the "goto" exception handling, which is default for `--mm:arc|orc` 
("setjmp" is used by default with `--mm:refc`). So unless you don't use 
exceptions, this is expected. There is the `--panics:on` switch which makes 
your program panics on "Defects" (index errors, out of mem etc…), this may 
remove some of this code at the price of not catching and not bubbling up 
defects, which are not catchable per the spec. Note that you can use 
`--exceptions:setjmp` with `--mm:arc|orc`.