Fix cancelling commands on <1.19 clients (#827)

proxy/src/main/java/com/velocitypowered/proxy/connection/client/ClientPlaySessionHandler.java

@@ -743,7 +743,8 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
                                                                          @Nullable SignedChatCommand signedCommand,
                                                                          Instant passedTimestamp) {
     IdentifiedKey playerKey = player.getIdentifiedKey();
-    if (result == CommandResult.denied() && playerKey != null) {
+    if (result == CommandResult.denied()) {
+      if (playerKey != null) {
         if (signedCommand != null && playerKey.getKeyRevision()
             .compareTo(IdentifiedKey.Revision.LINKED_V2) >= 0) {
           logger.fatal("A plugin tried to deny a command with signable component(s). "
@@ -752,6 +753,7 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
           player.disconnect(Component.text("A proxy plugin caused an illegal protocol state. "
               + "Contact your network administrator."));
         }
+      }
       return CompletableFuture.completedFuture(null);
     }