Fix cloning empty Maybe values in Javascript (#1080)

* Fix cloning empty Maybe values in Javascript

* Fix indent

* Remove branch name from js root binding

Author: dfellis

alan/test.ln

@@ -1250,6 +1250,13 @@ export fn{Test} main {
       test
         .assert(eq, maybe5.exists, true)
         .assert(eq, maybeNot.exists, false);
+    })
+    .it('can be cloned', fn (test: Mut{Testing}) {
+      const maybe5 = Maybe{i64}(5);
+      const maybeNot = Maybe{i64}();
+      test
+        .assert(eq, maybe5.clone.exists, true)
+        .assert(eq, maybeNot.clone.exists, false);
     });
 
   test.describe("Tree")

alan_std.js

@@ -130,7 +130,9 @@ export class FuzzySet {
 }
 
 export function clone(v) {
-  if (v instanceof Array) {
+  if (v === null) {
+    return null;
+  } else if (v instanceof Array) {
     return v.map(clone);
   } else if (v instanceof FuzzySet) {
     return v.union(new FuzzySet());