python: make print_debug_info robust when LD_LIBRARY_PATH is unset on Linux (microsoft#25704)

### Description

fixes microsoft#25700

---------

Co-authored-by: Copilot <[email protected]>

Author: 2 people

onnxruntime/__init__.py

@@ -215,9 +215,9 @@ def print_debug_info():
                 print(f"{package} not installed")
 
     if platform.system() == "Windows":
-        print(f"\nEnvironment variable:\nPATH={os.environ['PATH']}")
+        print(f"\nEnvironment variable:\nPATH={os.environ.get('PATH', '(unset)')}")
     elif platform.system() == "Linux":
-        print(f"\nEnvironment variable:\nLD_LIBRARY_PATH={os.environ['LD_LIBRARY_PATH']}")
+        print(f"\nEnvironment variable:\nLD_LIBRARY_PATH={os.environ.get('LD_LIBRARY_PATH', '(unset)')}")
 
     if importlib.util.find_spec("psutil"):