fix: sanitize experiment form data to prevent save failure on empty dates

components/ExperimentForm.tsx

@@ -66,7 +66,16 @@ const ExperimentForm: React.FC<ExperimentFormProps> = ({
 
     setLoading(true);
     try {
-      await createExperiment(formData);
+      // Sanitize optional fields
+      const submissionData = {
+        ...formData,
+        end_date: formData.end_date || undefined,
+        description: formData.description || undefined,
+        hypothesis: formData.hypothesis || undefined,
+        owner: formData.owner || undefined,
+      };
+
+      await createExperiment(submissionData);
       onSuccess();
       onClose();
     } catch (error: any) {