Closing certain types of windows creating lots of debug messages

[elcalenx]

While looking through system logs for some unrelated reason, I happened to notice a bunch of messages of the following kind:

org.gnome.Shell.desktop[18259]: X Error of failed request: BadWindow (invalid Window parameter)
org.gnome.Shell.desktop[18259]: Major opcode of failed request: 18 (X_ChangeProperty)
org.gnome.Shell.desktop[18259]: Resource id in failed request: 0x1a0010c
org.gnome.Shell.desktop[18259]: Serial number of failed request: 13
org.gnome.Shell.desktop[18259]: Current serial number in output stream: 15

After a little experimentation, I found they're occurring when I close certain types of windows, generally subordinate windows of various application (like, for example, Firefox's 'About' window), and they only seem to occur when Unite is enabled. As far as I can tell, everything still functions fine, despite these messages. While they seem fairly harmless, I do use software that makes use of lots of subordinate windows, so I'm getting a bunch of them in my logs...