early return for un-initialized heap

Author: robamu

src/tlsf.rs

@@ -112,6 +112,9 @@ impl Heap {
 
     fn free_with_cs(&self, cs: critical_section::CriticalSection) -> usize {
         let inner_mut = self.heap.borrow_ref_mut(cs);
+        if !inner_mut.initialized {
+            return 0;
+        }
         unsafe {
             inner_mut
                 .tlsf