diff --git a/webview/util.py b/webview/util.py
index <HASH>..<HASH> 100644
--- a/webview/util.py
+++ b/webview/util.py
@@ -65,10 +65,9 @@ def escape_string(string):
 
 
 def transform_url(url):
-    if url is None or ':' in url:
-        return url
-    else:
+    if url and ':' not in url:
         return 'file://' + os.path.abspath(url)
+    return url
 
 
 def make_unicode(string):
@@ -131,4 +130,4 @@ def inject_css(html, css):
     if '</html>' in html:
         return html.replace('</html>', style_tag + '</html>')
 
-    return style_tag + html
\ No newline at end of file
+    return style_tag + html
Fix transform_url logic

It should have been `':' in url` instead of `not in`. :D
Anyway I think this syntax reads better.