Fix UnboundLocalError when reading byte_stream #126

Job	Run time
mypy-strict	16s
pre-commit	17s
build_wheel_and_sdist	19s
test_on_supported_Pythons (3.10, windows-latest)	45s
test_on_supported_Pythons (3.9, macos-latest)	45s
test_on_supported_Pythons (3.11, ubuntu-24.04)	32s
test_on_supported_Pythons (3.10, macos-latest)	1m 52s
test_on_supported_Pythons (3.12, macos-latest)	1m 38s
test_on_supported_Pythons (3.9, windows-latest)	1m 4s
test_on_supported_Pythons (3.10, ubuntu-24.04)	35s
test_on_supported_Pythons (3.11, macos-latest)	1m 40s
test_on_supported_Pythons (3.9, ubuntu-24.04)	31s
test_on_supported_Pythons (3.14, macos-latest)	1m 6s
test_on_supported_Pythons (3.14, ubuntu-24.04)	43s
test_on_supported_Pythons (3.13, ubuntu-24.04)	31s
test_on_supported_Pythons (3.13, macos-latest)	1m 14s
test_on_supported_Pythons (3.11, windows-latest)	43s
test_on_supported_Pythons (3.13, windows-latest)	47s
test_on_supported_Pythons (3.14, windows-latest)	54s
test_on_supported_Pythons (3.12, ubuntu-24.04)	33s
test_on_supported_Pythons (3.12, windows-latest)	46s
	17m 31s

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