update minify.js

tool/minify.js

diff --git a/tool/minify.js b/tool/minify.js
index dd91596..828d9a9 100644
--- a/tool/minify.js
+++ b/tool/minify.js
@@ -38,6 +38,5 @@
 /// human-readable version.
 String getPreamble({bool minified: false, List<String> additionalGlobals: const []}) =>
     (minified ? _minified : _normal) +
-    (additionalGlobals == null ? "" :
-        additionalGlobals.map((global) => "self.\$global=\$global;").join());
-`);
\ No newline at end of file
+    (additionalGlobals.map((global) => "self.\$global=\$global;").join());
+`);