Version:           unspecified (using KDE 4.5.0) 
OS:                Linux

when i say blank space i mean a blank space where a virtual desktop could exist not the blank space you would see to the left and right (or above and bellow) when using 2 virtual desktops. For instance when using 3 virtual desktops the bottom right conner is blank.

this only happens with the desktop grid plug-in and with the present windows option enabled.

the crash occurs when dragging a desktop(by clicking on the background instead of a window) with at least one window on it over the blank space.


Reproducible: Always

Steps to Reproduce:
1) enable the desktop grid plugin with the "Use present windows effect to layout the windows" option enabled.
2)add 3 virtual desktop (lets assume the bottom right one is blank).
3) open up at least one window
4) drag the desktop containing the window over the blank space to the bottom right(by clicking and dragging on the background of the virtual desktop).
5) watch with dismay as your window borders disappear and screen flickers (kwin crashing).

Actual Results:  
crash

Expected Results:  
nothing.

heres the backtrace

Application: KWin (kwin), signal: Segmentation fault
[KCrash Handler]
#6  QHashData::firstNode (this=0x2c8fff8) at /usr/include/qt4/QtCore/qhash.h:187
#7  QHash<KWin::EffectWindow*, KWin::WindowMotionManager::WindowMotion>::begin (this=0x2c8fff8) at /usr/include/qt4/QtCore/qhash.h:460
#8  QHash<KWin::EffectWindow*, KWin::WindowMotionManager::WindowMotion>::keys (this=0x2c8fff8) at /usr/include/qt4/QtCore/qhash.h:646
#9  0x00007f45c027d717 in KWin::WindowMotionManager::managedWindows (this=0x13d3e30, e=<value optimized out>) at /var/tmp/portage/kde-base/kwin-4.5.0/work/kwin-4.5.0/kwin/lib/kwineffects.h:1661
#10 KWin::DesktopGridEffect::windowInputMouseEvent (this=0x13d3e30, e=<value optimized out>) at /var/tmp/portage/kde-base/kwin-4.5.0/work/kwin-4.5.0/kwin/effects/desktopgrid/desktopgrid.cpp:624
#11 0x00007f45ca809757 in KWin::EffectsHandlerImpl::checkInputWindowEvent (this=<value optimized out>, e=<value optimized out>)
    at /var/tmp/portage/kde-base/kwin-4.5.0/work/kwin-4.5.0/kwin/effects.cpp:897
#12 0x00007f45ca7b746d in KWin::Workspace::workspaceEvent (this=0x130a640, e=0x7fffdbcdfe70) at /var/tmp/portage/kde-base/kwin-4.5.0/work/kwin-4.5.0/kwin/events.cpp:260
#13 0x00007f45ca7962be in KWin::Application::x11EventFilter (this=0x7fffdbce0160, e=0x7fffdbcdfe70) at /var/tmp/portage/kde-base/kwin-4.5.0/work/kwin-4.5.0/kwin/main.cpp:363
#14 0x00007f45c9348ebb in qt_x11EventFilter (ev=0x7fffdbcdfe70) at kernel/qapplication_x11.cpp:409
#15 0x00007f45c9355c0c in QApplication::x11ProcessEvent (this=<value optimized out>, event=0x7fffdbcdfe70) at kernel/qapplication_x11.cpp:3243
#16 0x00007f45c937db8c in QEventDispatcherX11::processEvents (this=<value optimized out>, flags=) at kernel/qeventdispatcher_x11.cpp:132
#17 0x00007f45c8e0da0d in QEventLoop::processEvents (this=<value optimized out>, flags=) at kernel/qeventloop.cpp:149
#18 0x00007f45c8e0ddce in QEventLoop::exec (this=0x7fffdbce00c0, flags=) at kernel/qeventloop.cpp:201
#19 0x00007f45c8e1239a in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1003
#20 0x00007f45c92dba96 in QApplication::exec () at kernel/qapplication.cpp:3581
#21 0x00007f45ca798b3e in kdemain (argc=<value optimized out>, argv=<value optimized out>) at /var/tmp/portage/kde-base/kwin-4.5.0/work/kwin-4.5.0/kwin/main.cpp:531
#22 0x000000000040084d in main (argc=-607259120, argv=0x2c8fff8) at /var/tmp/portage/kde-base/kwin-4.5.0/work/kwin-4.5.0_build/kwin/kwin_dummy.cpp:3