Hide implicit constructor.

Author: toinehartman

rascal-lsp/src/main/java/org/rascalmpl/vscode/lsp/util/Nullables.java

@@ -35,6 +35,8 @@
  */
 public class Nullables {
 
+    private Nullables () { /* hide implicit constructor */}
+
     /**
      * Check a boolean value in a nullable object.
      * @param <A> The type of the containing object.