diff --git a/src/pocketmine/Player.php b/src/pocketmine/Player.php
index bbca13299..70f5e3344 100644
--- a/src/pocketmine/Player.php
+++ b/src/pocketmine/Player.php
@@ -3340,6 +3340,9 @@ class Player extends Human implements CommandSender, ChunkLoader, IPlayer{
 		$pk = new ModalFormRequestPacket();
 		$pk->formId = $id;
 		$pk->formData = json_encode($form);
+		if($pk->formData === false){
+			throw new \InvalidArgumentException("Failed to encode form JSON: " . json_last_error_msg());
+		}
 		if($this->dataPacket($pk)){
 			$this->forms[$id] = $form;
 		}
diff --git a/src/pocketmine/network/mcpe/PlayerNetworkSessionAdapter.php b/src/pocketmine/network/mcpe/PlayerNetworkSessionAdapter.php
index 5186cdd6a..adecfab3d 100644
--- a/src/pocketmine/network/mcpe/PlayerNetworkSessionAdapter.php
+++ b/src/pocketmine/network/mcpe/PlayerNetworkSessionAdapter.php
@@ -79,6 +79,10 @@ class PlayerNetworkSessionAdapter extends NetworkSession{
 	}
 
 	public function handleDataPacket(DataPacket $packet){
+		if(!$this->player->isConnected()){
+			return;
+		}
+
 		$timings = Timings::getReceiveDataPacketTimings($packet);
 		$timings->startTiming();