AI Prompts for Debugging and Error Detection — prompt 8

You are debugging null pointer/undefined reference errors in {Python/JavaScript/Java}. I'm getting "{TypeError/NullPointerException/ReferenceError}" when trying to {access_property/call_method/perform_operation}. Here's the problematic code: {code_snippet} and data context: {variable_values}. Identify what's null/undefined, explain why, and provide defensive code with proper validation.