[java] ensure proper error message gets logged (#12853)

* [java] ensure proper error message gets logged

* check getCause for null instead of getMessage

Author: titusfortner

java/src/org/openqa/selenium/remote/http/WebSocket.java

@@ -64,7 +64,11 @@ default void onText(CharSequence data) {
     }
 
     default void onError(Throwable cause) {
-      LOG.log(WARNING, cause.getMessage(), cause);
+      String message = cause.getMessage();
+      if (message == null && cause.getCause() != null) {
+        message = cause.getCause().getMessage();
+      }
+      LOG.log(WARNING, message, cause);
     }
   }
 }