fix(runtime): emit null for keyed root value

this is what jsonpath-plus does

Author: P0lip

src/__tests__/index.test.mjs

@@ -1430,6 +1430,28 @@ describe('Nimma', () => {
     });
   });
 
+  it('$..info^^', () => {
+    const document = {
+      info: {},
+    };
+
+    const collected = collect(document, ['$..info^^']);
+
+    expect(collected).to.deep.eq({});
+  });
+
+  it('$..info^~', () => {
+    const document = {
+      info: {},
+    };
+
+    const collected = collect(document, ['$..info^~']);
+
+    expect(collected).to.deep.eq({
+      '$..info^~': [[null, []]],
+    });
+  });
+
   forEach([
     Object.preventExtensions({
       shirts: Object.seal({

src/runtime/codegen-functions/in-bounds.mjs

@@ -1,5 +1,5 @@
 export default function (sandbox, pos, start, end, step) {
-  const value = sandbox.parentAt(-1);
+  const value = sandbox.valueAt(-1);
   const actualStart =
     start < 0
       ? Math.max(0, start + value.length)

src/runtime/sandbox.mjs

@@ -22,7 +22,7 @@ export class Sandbox {
     return dumpPath(this.#path);
   }
 
-  parentAt(i) {
+  valueAt(i) {
     return this.#history[this.#path.length + i];
   }
 

src/runtime/scope.mjs

@@ -117,8 +117,8 @@ export default class Scope {
     let path;
     let value;
     if (pos > 0) {
-      path = this.path.slice(0, Math.max(0, this.path.length - pos));
-      value = this.sandbox.parentAt(-pos);
+      path = this.path.slice(0, this.path.length - pos);
+      value = this.sandbox.valueAt(-pos);
     } else {
       path = this.path.slice();
       value = this.sandbox.value;
@@ -129,7 +129,7 @@ export default class Scope {
     } else {
       fn({
         path,
-        value: path.length === 0 ? void 0 : path[path.length - 1],
+        value: path.length === 0 ? null : path[path.length - 1],
       });
     }
   }