channels: Fix possible infinite loop in channel_read().

src/channels.c

@@ -2439,6 +2439,7 @@ int ssh_channel_read(ssh_channel channel, void *dest, uint32_t count, int is_std
   ssh_session session;
   ssh_buffer stdbuf;
   uint32_t len;
+  int rc;
 
   if(channel == NULL) {
       return SSH_ERROR;
@@ -2497,7 +2498,10 @@ int ssh_channel_read(ssh_channel channel, void *dest, uint32_t count, int is_std
       break;
     }
 
-    ssh_handle_packets(session, -2);
+    rc = ssh_handle_packets(session, -2);
+    if (rc != SSH_OK) {
+        return rc;
+    }
   }
 
   len = buffer_get_rest_len(stdbuf);