Fixes two compliation warnings (#2968)

Signed-off-by: Tao He <[email protected]>

Author: sighingnow

interactive_engine/executor/engine/pegasus/pegasus/src/communication/buffer.rs

@@ -118,7 +118,7 @@ impl<D: Data> BufSlotPtr<D> {
     fn destroy(&mut self) {
         unsafe {
             let ptr = self.ptr;
-            Box::from_raw(ptr.as_ptr());
+            drop(Box::from_raw(ptr.as_ptr()));
         }
     }
 }

interactive_engine/executor/store/exp_store/src/graph_db/csr_topo.rs

@@ -44,7 +44,7 @@ impl<I: IndexType> MutEdgeVec<I> {
         let mut num_edges = 0;
         // will be sorted via label
         for label in adj.keys().cloned().sorted() {
-            for vec in adj.get_mut(&label) {
+            if let Some(vec) = adj.get_mut(&label) {
                 vec.sort();
                 self.offsets[node]
                     .inner