fix(EnvironmentParser): reduced crashes if no Classifiers are found (#441)

fixes #440

Signed-off-by: Jan Kowalleck <jan.kowalleck@gmail.com>

Author: jkowalleck

cyclonedx_py/parser/environment.py

@@ -75,7 +75,7 @@ def __init__(self, use_purl_bom_ref: bool = False) -> None:
                 # Therefore, just go with a named license.
                 c.licenses.add(LicenseChoice(license_=License(license_name=i_metadata['License'])))
 
-            for classifier in i_metadata.get_all("Classifier"):
+            for classifier in i_metadata.get_all("Classifier", []):
                 # Trove classifiers - https://packaging.python.org/specifications/core-metadata/#metadata-classifier
                 # Full list: https://pypi.python.org/pypi?%3Aaction=list_classifiers
                 if str(classifier).startswith('License :: OSI Approved :: '):