Comment 7 for bug 978511

Not sure it it is related or not but I received similar errors in a terminal while testing but did not get a crash. I had received a long list of errors:

Many like this:
warning : (/build/buildd/cairo-dock-3.0.0.1/src/gldit/cairo-dock-applications-manager.c:cairo_dock_create_surface_from_xpixmap:1231)
  No thumbnail available.
Either the WM doesn't support this functionnality, or the window was minimized when the dock has been launched.

Many like this:
kbuildsycoca4(25248) KBuildServiceFactory::createEntry: Invalid Service : "/usr/share/xubuntu/applications/Thunar.desktop"
kbuildsycoca4(25248) KConfigGroup::readXdgListEntry: List entry MimeType in ".hidden/kommander.desktop" is not compliant with XDG standard (missing trailing semicolon).
kbuildsycoca4(25248) KConfigGroup::readXdgListEntry: List entry x-scheme-handler/file in "/home/brian/.local/share/applications/mimeapps.list" is not compliant with XDG standard (missing trailing semicolon).
kbuildsycoca4(25248) KConfigGroup::readXdgListEntry: List entry x-scheme-handler/trash in "/home/brian/.local/share/applications/mimeapps.list" is not compliant with XDG standard (missing trailing semicolon).

and finally these:
X Error: BadWindow (invalid Window parameter) 3
  Major opcode: 20 (X_GetProperty)
  Resource id: 0x460140f
X Error: BadWindow (invalid Window parameter) 3
  Major opcode: 20 (X_GetProperty)
  Resource id: 0x460140f
X Error: BadWindow (invalid Window parameter) 3
  Major opcode: 18 (X_ChangeProperty)
  Resource id: 0x460140f

I copied everything and pasted it into a gedit window (I have attached the file) then saved and closed gedit. Then when I went back to the terminal I had this error:
warning : (/build/buildd/cairo-dock-plug-ins-3.0.0.1/GMenu/src/applet-util.c:cd_expand_field_codes:120)
  Unexpected field code %U in exec string 'gedit %U' : cannot handle file or url codes in the menu.

Realizing that I had gedit open and it appeared in the dock as an icon I thought about what I had opened kde related for the other messages (given the kbuildsycoca4 and kommander.desktop references I assume it was KDE related) and realized that I was playing a kde game while waiting for my youtube-dl to complete (I was testing functionality for queued up urls).

This may not be related but there are many similarities.