Description of problem:
The bug is simply triggered by removing the notebook (Dell Latitude 6400) from a dockingstation with an external monitor attached.

Additional info:
WARNING: at drivers/gpu/drm/i915/intel_dp.c:1910 intel_dp_link_down+0x1d2/0x1e0 [i915]()
Hardware name: Latitude E6400                  
Modules linked in: cdc_wdm cdc_acm hidp fuse ebtable_nat ipt_MASQUERADE nf_conntrack_netbios_ns nf_conntrack_broadcast be2iscsi iscsi_boot_sysfs ip6table_mangle ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 bnx2i cnic uio cxgb4i cxgb4 cxgb3i cxgb3 mdio libcxgbi ib_iser iptable_nat nf_nat_ipv4 nf_nat rdma_cm ib_addr iw_cm ib_cm ib_sa ib_mad iptable_mangle ib_core iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack ebtable_filter ebtables ip6table_filter ip6_tables rfcomm bnep btusb bluetooth iTCO_wdt iTCO_vendor_support dell_wmi sparse_keymap coretemp dell_laptop dcdbas snd_hda_codec_hdmi microcode snd_hda_codec_idt snd_hda_intel snd_hda_codec joydev snd_hwdep snd_seq i2c_i801 snd_seq_device snd_pcm arc4 lpc_ich mfd_core iwldvm mac80211 snd_page_alloc iwlwifi cfg80211 rfkill snd_timer snd soundcore vhost_net tun macvtap macvlan kvm_intel kvm uinput dm_crypt usb_storage firewire_ohci sdhci_pci sdhci i915 mmc_core firewire_core crc_itu_t i2c_algo_bit drm_kms_helper e1000e drm i2c_core wmi video hid_logitech_dj sunrpc
Pid: 864, comm: Xorg Not tainted 3.7.4-204.fc18.x86_64 #1
Call Trace:
 [<ffffffff8105e67f>] warn_slowpath_common+0x7f/0xc0
 [<ffffffff8105e6da>] warn_slowpath_null+0x1a/0x20
 [<ffffffffa017bab2>] intel_dp_link_down+0x1d2/0x1e0 [i915]
 [<ffffffffa017dc64>] intel_disable_dp+0x44/0x170 [i915]
 [<ffffffffa016c232>] i9xx_crtc_disable+0x162/0x180 [i915]
 [<ffffffffa01719c7>] intel_crtc_update_dpms+0x77/0xb0 [i915]
 [<ffffffffa0171aba>] intel_encoder_dpms+0x1a/0x30 [i915]
 [<ffffffffa017310c>] intel_connector_dpms+0x3c/0x70 [i915]
 [<ffffffffa00ce9cd>] drm_mode_obj_set_property_ioctl+0x32d/0x340 [drm]
 [<ffffffffa00cea10>] drm_mode_connector_property_set_ioctl+0x30/0x40 [drm]
 [<ffffffffa00bd4a3>] drm_ioctl+0x4d3/0x580 [drm]
 [<ffffffff8118fb81>] ? mem_cgroup_bad_page_check+0x21/0x30
 [<ffffffffa00ce9e0>] ? drm_mode_obj_set_property_ioctl+0x340/0x340 [drm]
 [<ffffffff8117f689>] ? kfree+0x49/0x170
 [<ffffffff8117f689>] ? kfree+0x49/0x170
 [<ffffffff811a61e9>] do_vfs_ioctl+0x99/0x580
 [<ffffffff8128b9da>] ? inode_has_perm.isra.31.constprop.61+0x2a/0x30
 [<ffffffff8128cda7>] ? file_has_perm+0x97/0xb0
 [<ffffffff811a6761>] sys_ioctl+0x91/0xb0
 [<ffffffff810dc78c>] ? __audit_syscall_exit+0x3ec/0x450
 [<ffffffff8163e059>] system_call_fastpath+0x16/0x1b