fix: comparison for empty/nil, fixes #321

src/util/literal.ts

@@ -2,11 +2,12 @@ import { NullDrop } from '../drop/null-drop'
 import { EmptyDrop } from '../drop/empty-drop'
 import { BlankDrop } from '../drop/blank-drop'
 
+const nil = new NullDrop()
 export const literalValues = {
   'true': true,
   'false': false,
-  'nil': new NullDrop(),
-  'null': new NullDrop(),
+  'nil': nil,
+  'null': nil,
   'empty': new EmptyDrop(),
   'blank': new BlankDrop()
 }