In rare cases node can be no member of busylist

Author: rPraml

ebean-datasource/src/main/java/io/ebean/datasource/pool/ConnectionBuffer.java

@@ -177,10 +177,12 @@ void addFree(PooledConnection pc) {
      * Returns true, if this connection was part of the busy list or false, if not (or removed twice)
      */
     boolean removeBusy(PooledConnection c) {
-        if (c.busyNode() == null) {
+        Node node = c.busyNode();
+        if (node == null || node.next == null) {
+            // node is not yet or no longer in busy list
             return false;
         }
-        c.busyNode().remove();
+        node.remove();
         busySize--;
         c.setBusyNode(null);
         return true;