Fix IndexError in litellm's ollama_pt function when using Ollama/Qwen models with tools

This patch addresses issue #2744 by adding bounds checking before accessing
messages[msg_i].get('tool_calls') in the ollama_pt function. The issue occurs
when an assistant message is the last message in the list, causing msg_i to
go out of bounds.

The fix is implemented as a monkey patch in CrewAI to avoid waiting for
an upstream fix in litellm.

Co-Authored-By: Joe Moura <joao@crewai.com>

tests/patches/test_litellm_patch.py

@@ -0,0 +1,45 @@
+"""
+Test for the litellm patch that fixes the IndexError in ollama_pt function.
+"""
+
+import unittest
+from unittest.mock import patch, MagicMock
+import sys
+
+import litellm
+from litellm.litellm_core_utils.prompt_templates.factory import ollama_pt
+
+from crewai.patches.litellm_patch import patch_litellm_ollama_pt
+
+
+class TestLitellmPatch(unittest.TestCase):
+    def test_ollama_pt_patch_fixes_index_error(self):
+        """Test that the patch fixes the IndexError in ollama_pt."""
+        # Create a message list where the assistant message is the last one
+        messages = [
+            {"role": "user", "content": "Hello"},
+            {"role": "assistant", "content": "Hi there"},
+        ]
+        
+        # Store the original function to restore it after the test
+        original_ollama_pt = litellm.litellm_core_utils.prompt_templates.factory.ollama_pt
+        
+        try:
+            # Apply the patch
+            patch_litellm_ollama_pt()
+            
+            # The patched function should not raise an IndexError
+            result = ollama_pt("qwen3:4b", messages)
+            
+            # Verify the result is as expected
+            self.assertIn("prompt", result)
+            self.assertIn("images", result)
+            self.assertIn("### User:\nHello", result["prompt"])
+            self.assertIn("### Assistant:\nHi there", result["prompt"])
+        finally:
+            # Restore the original function to avoid affecting other tests
+            litellm.litellm_core_utils.prompt_templates.factory.ollama_pt = original_ollama_pt
+
+
+if __name__ == "__main__":
+    unittest.main()