fix: handle None values in token counter

- Update sum_cached_prompt_tokens to handle None values gracefully
- Add unit tests for token counting with None values
- Fixes #2197

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

src/crewai/agents/agent_builder/utilities/base_token_process.py

@@ -17,8 +17,9 @@ class TokenProcess:
         self.completion_tokens += tokens
         self.total_tokens += tokens
 
-    def sum_cached_prompt_tokens(self, tokens: int) -> None:
+    def sum_cached_prompt_tokens(self, tokens: int | None) -> None:
-        self.cached_prompt_tokens += tokens
+        if tokens is not None:
+            self.cached_prompt_tokens += tokens
 
     def sum_successful_requests(self, requests: int) -> None:
         self.successful_requests += requests

tests/utilities/test_token_process.py

@@ -0,0 +1,17 @@
+import unittest
+from crewai.agents.agent_builder.utilities.base_token_process import TokenProcess
+
+
+class TestTokenProcess(unittest.TestCase):
+    def setUp(self):
+        self.token_process = TokenProcess()
+
+    def test_sum_cached_prompt_tokens_with_none(self):
+        initial_tokens = self.token_process.cached_prompt_tokens
+        self.token_process.sum_cached_prompt_tokens(None)
+        self.assertEqual(self.token_process.cached_prompt_tokens, initial_tokens)
+
+    def test_sum_cached_prompt_tokens_with_int(self):
+        initial_tokens = self.token_process.cached_prompt_tokens
+        self.token_process.sum_cached_prompt_tokens(5)
+        self.assertEqual(self.token_process.cached_prompt_tokens, initial_tokens + 5)