refactor: error handling (#41)

mini-lsm-starter/src/lsm_iterator.rs

@@ -46,11 +46,15 @@ impl StorageIterator for LsmIterator {
 /// `is_valid` should return false, and `next` should always return an error.
 pub struct FusedIterator<I: StorageIterator> {
     iter: I,
+    has_errored: bool,
 }
 
 impl<I: StorageIterator> FusedIterator<I> {
     pub fn new(iter: I) -> Self {
-        Self { iter }
+        Self {
+            iter,
+            has_errored: false,
+        }
     }
 }