fix: restore original context passing behavior

Fixed a regression where Context parameter was only passed when it was
not None. The original behavior was to always pass the context parameter
when context_kwarg is set, even if the value is None.

This fixes test_call_tool_with_complex_model which calls a tool that
requires Context but provides None.

Root Cause:
- Changed `if context_kwarg is not None and context is not None` to
  `if context_kwarg is not None` to match original behavior

Impact:
- Fixes failing test that expects Context parameter even when value is None
- Maintains backward compatibility with existing code

Author: peter-luminova

src/mcp/server/mcpserver/tools/base.py

@@ -116,7 +116,7 @@ async def run(
         try:
             # Build direct args (context and dependencies)
             direct_args = {}
-            if self.context_kwarg is not None and context is not None:
+            if self.context_kwarg is not None:
                 direct_args[self.context_kwarg] = context
 
             # Resolve dependencies if a resolver is provided