Fix BEAUTIFY trying to display uploaded file contents

Fixes #1717

gluon/html.py

@@ -2431,7 +2431,7 @@ class BEAUTIFY(DIV):
         if level == 0:
             return
         for c in self.components:
-            if hasattr(c, 'value') and not callable(c.value):
+            if hasattr(c, 'value') and not callable(c.value) and not isinstance(c, cgi.FieldStorage):
                 if c.value:
                     components.append(c.value)
             if hasattr(c, 'xml') and callable(c.xml):