Fix for when global and window object both not found.

Changes:

* use globalThis polyfill

lib/handlebars/no-conflict.js

@@ -1,30 +1,23 @@
-/* global global, window */
+/* global globalThis */
 export default function(Handlebars) {
-  function getRoot() {
-    if (typeof global !== 'undefined') {
-      return global;
-    } else if (typeof window !== 'undefined') {
-      return window;
-    }
-
-    return null;
-  }
+  /* istanbul ignore next */
+  // https://mathiasbynens.be/notes/globalthis
+  (function() {
+    if (typeof globalThis === 'object') return;
+    Object.prototype.__defineGetter__('__magic__', function() {
+      return this;
+    });
+    __magic__.globalThis = __magic__; // eslint-disable-line no-undef
+    delete Object.prototype.__magic__;
+  })();
 
-  const root = getRoot();
+  const $Handlebars = globalThis.Handlebars;
 
-  if (root !== null) {
-    root.$Handlebars = root.Handlebars;
-
-    /* istanbul ignore next */
-    Handlebars.noConflict = function() {
-      if (root.Handlebars === Handlebars) {
-        root.Handlebars = root.$Handlebars;
-      }
-      return Handlebars;
-    };
-  } else {
-    Handlebars.noConflict = function() {
-      return Handlebars;
-    };
-  }
+  /* istanbul ignore next */
+  Handlebars.noConflict = function() {
+    if (globalThis.Handlebars === Handlebars) {
+      globalThis.Handlebars = $Handlebars;
+    }
+    return Handlebars;
+  };
 }