Fix potential assertion error introduced by 0bc93dd

Motivation:
Commit 0bc93dd introduced a potential assertion failure, if the deprecated method would be used.

Modifications:
Fix the potential assertion error.

Result:
Regression removed

transport/src/main/java/io/netty/channel/nio/AbstractNioChannel.java

@@ -159,7 +159,10 @@ public abstract class AbstractNioChannel extends AbstractChannel {
                 });
             }
         } else {
-            setReadPending0(readPending);
+            // Best effort if we are not registered yet clear readPending.
+            // NB: We only set the boolean field instead of calling clearReadPending0(), because the SelectionKey is
+            // not set yet so it would produce an assertion failure.
+            this.readPending = readPending;
         }
     }