Snap sync: fix downloader not being "freed" on empty responses (#4101)

**Motivation**

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**Description**

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introduces -->

<!-- Link to issues: Resolves #111, Resolves #222 -->

Closes #issue_number

Author: juan518munoz

crates/networking/p2p/peer_handler.rs

@@ -873,6 +873,10 @@ impl PeerHandler {
             }
 
             if let Ok((accounts, peer_id, chunk_start_end)) = task_receiver.try_recv() {
+                downloaders.entry(peer_id).and_modify(|downloader_is_free| {
+                    *downloader_is_free = true;
+                });
+
                 if let Some((chunk_start, chunk_end)) = chunk_start_end {
                     if chunk_start <= chunk_end {
                         tasks_queue_not_started.push_back((chunk_start, chunk_end));
@@ -904,10 +908,6 @@ impl PeerHandler {
                         .iter()
                         .map(|unit| AccountState::from(unit.account.clone())),
                 );
-
-                downloaders.entry(peer_id).and_modify(|downloader_is_free| {
-                    *downloader_is_free = true;
-                });
             }
 
             // Check if any dump account task finished
@@ -1233,6 +1233,11 @@ impl PeerHandler {
                     remaining_start,
                     remaining_end,
                 } = result;
+
+                downloaders.entry(peer_id).and_modify(|downloader_is_free| {
+                    *downloader_is_free = true;
+                });
+
                 if remaining_start < remaining_end {
                     tasks_queue_not_started.push_back((remaining_start, remaining_end));
                 } else {
@@ -1256,10 +1261,6 @@ impl PeerHandler {
                 for (i, bytecode) in bytecodes.into_iter().enumerate() {
                     all_bytecodes[start_index + i] = bytecode;
                 }
-
-                downloaders.entry(peer_id).and_modify(|downloader_is_free| {
-                    *downloader_is_free = true;
-                });
             }
 
             let peer_channels = self