nullable fix

app.py

@@ -79,12 +79,16 @@ class AdvancedReasoningTool(Tool):
         "problem_type": {
             "type": "string", 
             "description": "Type of problem (e.g., 'logical', 'mathematical', 'analytical', 'research')",
+            "nullable": True
         }
     }
     
     output_type = "string"
 
-    def forward(self, problem: str, problem_type: str = "general"):
+    def forward(self, problem: str, problem_type: str = None):
+        if problem_type is None:
+            problem_type = "general"
+            
         reasoning_frameworks = {
             "logical": "1. Identify premises\n2. Apply logical rules\n3. Check for contradictions\n4. Draw conclusions",
             "mathematical": "1. Understand what's being asked\n2. Identify known values\n3. Choose appropriate formulas\n4. Calculate step-by-step\n5. Verify the answer",