[Bug]: tokenize emits a non-existent new line token for empty input

Describe the bug

When using token.generate_tokens() on an empty string, a NL token is returned when no such token exists for CPython. The return token also spans a non-existent length, which caused stubgen-pyx to crash. Only effects "", # ... and "\n" were fine. This caused stubgen-pyx to crash on an otherwise empty file.

Likely occurs in GraalPy's re-implementation of _tokenize.TokenizerIter

Operating system

Linux

CPU architecture

x86_64

GraalPy version

GraalPy 3.13.14 (GraalVM CE Native 25.3.4.1)

JDK version

openjdk 25.0.4 2026-07-21 LTS (Temurin-25.0.4+7)

Context configuration

N/A

Steps to reproduce

# repro.py
import io, tokenize
for tok in tokenize.generate_tokens(io.StringIO("").readline):
    print(tok)

$ graalpy repro.py
TokenInfo(type=63 (NL), string='', start=(1, 0), end=(1, 1), line='')
TokenInfo(type=0 (ENDMARKER), string='', start=(2, 0), end=(2, 0), line='')

$ python3.13 repro.py          # and python3.14, identical
TokenInfo(type=0 (ENDMARKER), string='', start=(1, 0), end=(1, 0), line='')

Native version

import io, _tokenize
for t in _tokenize.TokenizerIter(io.StringIO("").readline, extra_tokens=True):
    print(t)
#GraalPy 3.13.14:  (63, '', (1, 0), (1, 1), '')      ← phantom NL
#                  (0,  '', (2, 0), (2, 0), '')
#CPython 3.13:     (0,  '', (1, 0), (1, 0), '')

Expected behavior

Should match the same output as CPython 3.13, and not emit non-existent spans.

Stack trace

N/A

Additional context

N/A

Start by running the repro.py example with GraalPy and CPython, then trace the GraalPy implementation of _tokenize.TokenizerIter used by tokenize.generate_tokens. The fix is done when empty input produces only the CPython-compatible ENDMARKER with matching positions, while the existing comment and newline cases remain correct.