Handle BigInt in MOZ_TO_ME

Author: sbc100

lib/mozilla-ast.js

@@ -555,6 +555,13 @@ import {
                 return new AST_Number(args);
               case "boolean":
                 return new (val ? AST_True : AST_False)(args);
+              case "bigint":
+                args.value = val;
+                return new AST_BigInt(args);
+              case "undefined":
+                return undefined;
+              default:
+                throw new Error("Unhandled value type: " + typeof val);
             }
         },
         MetaProperty: function(M) {