Unhandled exception: value of of range
### Version

Nightly

### Category

Major — The software does not fulfill the task it is designed for.

### Steps to Reproduce

1. open a nim-file in moe. (content: echo "test" )
2. type :run
3. see nothing happen
4. press arrow-down

### Detailed Description

output:
fatal.nim(54)            sysFatal
                                     Error: unhandled exception: value out of range: -1 notin 0 .. 9223372036854775807 [RangeDefect]
                                            
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using latest moe@#head