fix: handle null values to disable outputs

Co-authored-by: aider (openai/andrew/openrouter/deepseek/deepseek-chat-v3.1) <aider@aider.chat>

src/meta_plugin/mod.rs

@@ -141,6 +141,12 @@ pub enum MetaPluginType {
 pub fn process_metadata_outputs(internal_name: &str, value: serde_yaml::Value, outputs: &std::collections::HashMap<String, serde_yaml::Value>) -> Option<MetaData> {
     // Check if this output is disabled
     if let Some(mapping) = outputs.get(internal_name) {
+        // Check for null to disable the output
+        if mapping.is_null() {
+            debug!("META: Skipping disabled output (null): {}", internal_name);
+            return None;
+        }
+        // Check for boolean false to disable the output
         if let Some(false_val) = mapping.as_bool() {
             if !false_val {
                 debug!("META: Skipping disabled output: {}", internal_name);