declare artifact_content variable to avoid reference before assignmen…

…t in case of exception (#1554)

in case the content is not UTF-8 encoded an exception will be raised and artifact_content will never be assigned, this cause the task to fail with a misleading exception: `[local variable 'artifact_content' referenced before assignment]`, while it should be `Artifact {evidence.artifact_name} has empty content or not UTF-8 encoded`

turbinia/workers/analysis/llm_analyzer.py

@@ -105,6 +105,7 @@ def run(self, evidence, result):
       open_function = gzip.open
 
     # Read the input file
+    artifact_content = None
     try:
       with open_function(evidence.local_path, "rb") as input_file:
         artifact_content = input_file.read().decode("utf-8")