Adding handler check to task roots check and fixing clippy errors

Author: udesou

mmtk/src/julia_scanning.rs

@@ -248,7 +248,8 @@ pub unsafe fn scan_julia_object<SV: SlotVisitor<JuliaVMSlot>>(obj: Address, clos
 
             #[cfg(debug_assertions)]
             {
-                if !cfg!(feature = "non_moving") {
+                let eh = (*ta).eh;
+                if !cfg!(feature = "non_moving") && !eh.is_null() {
                     // Panic if task has not been processed as root
                     use crate::scanning::TASK_ROOTS;
                     let task_roots = TASK_ROOTS.lock().unwrap();

mmtk/src/scanning.rs

@@ -203,15 +203,12 @@ impl Scanning<JuliaVM> for VMScanning {
         // that have been processed before
         while !extra_root_tasks.is_empty() {
             let root_task = extra_root_tasks.pop();
-            match root_task {
-                Some(t) => {
-                    if !TASK_ROOTS.lock().unwrap().contains(&t) {
-                        let task_address = t.to_raw_address();
-                        let task = task_address.to_ptr::<_jl_task_t>();
-                        root_scan_task(task, false, &mut extra_root_tasks);
-                    }
+            if let Some(t) = root_task {
+                if !TASK_ROOTS.lock().unwrap().contains(&t) {
+                    let task_address = t.to_raw_address();
+                    let task = task_address.to_ptr::<_jl_task_t>();
+                    root_scan_task(task, false, &mut extra_root_tasks);
                 }
-                None => {}
             }
         }