IndexError: list index out of range
This line explodes very frequently, without useful debug information:

```
  File "/home/juan/.local/lib/python3.9/site-packages/nimporter.py", line 48, in __init__
    nim_module = nim_module.splitlines()[-1]
IndexError: list index out of range

```

Full traceback

```console
>>> import faster_than_walk
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/juan/.local/lib/python3.9/site-packages/faster_than_walk/__init__.py", line 7, in <module>
    from . faster_than_walk import *
  File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
  File "<frozen importlib._bootstrap>", line 982, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 925, in _find_spec
  File "/home/juan/.local/lib/python3.9/site-packages/nimporter.py", line 1150, in find_spec
    return Nimporter.import_nim_code(fullname, path, library=False)
  File "/home/juan/.local/lib/python3.9/site-packages/nimporter.py", line 828, in import_nim_code
    NimCompiler.compile_nim_code(
  File "/home/juan/.local/lib/python3.9/site-packages/nimporter.py", line 588, in compile_nim_code
    raise NimCompileException(errors[0])
  File "/home/juan/.local/lib/python3.9/site-packages/nimporter.py", line 48, in __init__
    nim_module = nim_module.splitlines()[-1]
IndexError: list index out of range

>>> exit()

$ ls /home/juan/.local/lib/python3.9/site-packages/faster_than_walk/
faster_than_walk.nim  faster_than_walk.nim.cfg  __init__.py

$ head /home/juan/.local/lib/python3.9/site-packages/faster_than_walk/faster_than_walk.nim
import os, strutils, nimpy


proc walk*(folderpath: string, extensions: seq[string] = @[""], followlinks : bool = false, yieldfiles: bool = true, debugs: bool = false, check_folders: bool = false): seq[string] {.exportpy.} =
  ## Faster os.walk(), followlinks follows SymLinks, yieldfiles yields files else folders, return 1 list of strings.
  let extused {.noalias.} = create(bool, sizeOf(bool))  # Optimization.
  extused[] = extensions != @[""] and extensions.len > 0
  for item in walkDirRec(folderpath, {if yieldfiles: pcFile else: pcDir}, {if followlinks: pcLinkToDir else: pcDir}, checkDir=check_folders):
    if unlikely(debugs): echo item
    if unlikely(extused[]):

$
```

- https://github.com/Pebaz/nimporter/blob/master/nimporter.py#L49

It is possible to add some defensive programing just on that line ?,
something like a `try  except` and `print` a useful message, 
manually checking like 
`if not len(nim_module) > 0: print("ERROR: File not found, Nimporter can not find the nim files")` or something.
