Correct hashcode method.

src/com/dmdirc/util/collections/EquatableWeakReference.java

 
 import java.lang.ref.Reference;
 import java.lang.ref.WeakReference;
-import java.util.Objects;
 
 /**
  * An extension of WeakReference that implements a sane equals and hashcode
 
     @Override
     public int hashCode() {
-        return Objects.hash(get());
+        if (get() == null) {
+            return 0;
+        }
+        return get().hashCode();
     }
 
 }