Fix: Handle empty queries in TavilySearchRM to prevent "Query is missing" error (#362)

[IsmailMabrouki]

Description

Fixes #362 - "Query is missing" error when using TavilySearchRM with MCP servers

This PR adds comprehensive input validation to TavilySearchRM.forward() to handle empty, None, or invalid queries gracefully.

Problem

Users reported getting "Query is missing" errors when integrating STORM with MCP (Model Context Protocol) servers. The error occurred when empty or None queries were passed to the Tavily search API.

Solution

• ✅ Input Validation: Added checks for empty, None, or whitespace-only queries
• ✅ List Filtering: For list inputs, filter out invalid queries and keep only valid ones
• ✅ Graceful Handling: Return empty results instead of crashing
• ✅ Error Handling: Added try-catch around the Tavily API call
• ✅ Debug Support: Added informative warning messages

Changes Made

• Modified knowledge_storm/rm.py in TavilySearchRM.forward() method
• Added comprehensive input validation before API calls
• Added error handling around tavily_client.search(query)

Testing

The fix correctly handles:

• Empty strings ("")
• Whitespace-only strings (" ")
• None values
• Empty lists ([])
• Lists with mixed valid/invalid queries
• Valid queries (unchanged behavior)

Backward Compatibility

✅ This change is fully backward compatible - all existing valid use cases continue to work exactly as before.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)