Fix FileBrowser: do not show 'advanced filter' panel outside of lib browsing context,

it’s only used there so far.

Reported by Thomas Beck (plasmasolutions) over IRC, thanks.

Safe enough for 2.76.

release/scripts/startup/bl_ui/space_filebrowser.py

@@ -229,6 +229,11 @@ class FILEBROWSER_PT_advanced_filter(Panel):
     bl_category = "Filter"
     bl_label = "Advanced Filter"
 
+    @classmethod
+    def poll(cls, context):
+        # only useful in append/link (library) context currently...
+        return context.space_data.params.use_library_browsing
+
     def draw(self, context):
         layout = self.layout
         space = context.space_data