fix: add input validation to send_message_tool to prevent crashes

[sprmn24]

What does this PR do?

This PR adds input validation to send_message_tool to prevent crashes when invalid or malformed arguments are passed.

Currently, the function assumes args is always a dictionary. However, in real-world usage (e.g. LLM outputs, external gateways like Telegram/Discord), this assumption may not hold. If args is None or not a dictionary, calling .get() results in:

AttributeError: 'NoneType' object has no attribute 'get'

This PR ensures safer handling of such cases by validating input before usage.

Related Issue

No related issue

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 🔒 Security fix
• 📝 Documentation update
• ✅ Tests (adding or improving test coverage)
• 🔄 Refactor (no behavior change)
• 🎯 New skill (bundled or hub)

Changes Made

• Added type validation for args in tools/send_message_tool.py
• Prevented .get() calls on non-dictionary inputs
• Returned safe JSON error response instead of raising runtime exceptions

How to Test

1. Call send_message_tool with valid dictionary input → should behave normally
2. Call send_message_tool(None) → should return JSON error instead of crashing
3. Call send_message_tool("invalid") → should return JSON error safely