Fix an assertion error introduced by 0bc93dda08

Motivation:
    
Commit 0bc93dda08 introduced an assertion
failure.

Modifications:

Fix the assertion error.

Result:

Regression removed

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

@@ -176,7 +176,9 @@ public abstract class AbstractNioChannel extends AbstractChannel {
             }
         } else {
             // Best effort if we are not registered yet clear readPending. This happens during channel initialization.
-            clearReadPending0();
+            // 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.
+            readPending = false;
         }
     }