Throw a caught exception instead of doing nothing (#12979)

Motivation:
An exception has been caught and ignored.

Modification:
Throw the caught exception to make it useful.

Result: 
Not swallow exception

Co-authored-by: Norman Maurer <norman_maurer@apple.com>

buffer/src/main/java/io/netty5/buffer/DefaultCompositeBuffer.java

@@ -64,6 +64,9 @@ public void drop(DefaultCompositeBuffer buf) {
                     }
                 }
             }
+            if (re != null) {
+                throw re;
+            }
         }
 
         @Override