Fix linting and type-checking issues

- Fix whitespace in docstring blank lines (ruff W293)
- Add null check before calling _validate_base_url to fix mypy type error
- Ensure url_to_validate is not None before validation

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

src/crewai/llm.py

@@ -1200,7 +1200,7 @@ class LLM(BaseLLM):
         # Validate base_url for Ollama connections
         if "ollama" in self.model.lower() and (self.base_url or self.api_base):
             url_to_validate = self.base_url or self.api_base
-            if not self._validate_base_url(url_to_validate):
+            if url_to_validate and not self._validate_base_url(url_to_validate):
                 raise ValueError(
                     f"Invalid Ollama base_url: '{url_to_validate}'. "
                     "Please check that the URL format is correct and the IP address is valid. "
@@ -1217,8 +1217,8 @@ class LLM(BaseLLM):
             bool: True if URL is valid, False otherwise
         """
         try:
-            from urllib.parse import urlparse
             import ipaddress
+            from urllib.parse import urlparse
 
             result = urlparse(url)