allow omission of 'label' section in status bar applet definitions

This solves the following error reported by Tom Kazimiers:

E, [2010-01-03T23:09:33.778367 #4260] ERROR -- : undefined method
`label' for #<#<Class:0x7f1ae97e6bd8>::Status:0x7f1aea1e4720>
(NoMethodError)

display/status.yaml

@@ -44,10 +44,9 @@ script:
               CONFIG.origin(code, "display:status:#{name}:script")
           end
 
-          if code = definition['label']
-            instance_eval "def label; #{code}; end",
-              CONFIG.origin(code, "display:status:#{name}:label")
-          end
+          code = definition['label']
+          instance_eval "def label; #{code}; end",
+            CONFIG.origin(code, "display:status:#{name}:label")
 
           # buttons appear in ASCII order of their IXP file name
           # so prepend a number to get ordered status bar applets