db exception

See the end of this message for details on invoking
just-in-time (JIT) debugging instead of this dialog box.

************** Exception Text **************
System.NullReferenceException: Object reference not set to an instance of an object.
   at CodeImp.DoomBuilder.Controls.FieldsEditorControl.Apply(UniFields tofields)
   at CodeImp.DoomBuilder.Windows.SectorEditForm.apply_Click(Object sender, EventArgs e)
   at System.Windows.Forms.Control.OnClick(EventArgs e)
   at System.Windows.Forms.Button.OnClick(EventArgs e)
   at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
   at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ButtonBase.WndProc(Message& m)
   at System.Windows.Forms.Button.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)


************** Loaded Assemblies **************
mscorlib
    Assembly Version: 2.0.0.0
    Win32 Version: 2.0.50727.8784 (WinRel.050727-8700)
    CodeBase: file:///C:/Windows/Microsoft.NET/Framework/v2.0.50727/mscorlib.dll
----------------------------------------
Builder
    Assembly Version: 2.1.2.1553
    Win32 Version: 2.1.2.1553
    CodeBase: file:///D:/Programs/Doom%20Builder%202/Builder.exe
----------------------------------------
System
    Assembly Version: 2.0.0.0
    Win32 Version: 2.0.50727.8793 (WinRelRS2.050727-8700)
    CodeBase: file:///C:/WINDOWS/assembly/GAC_MSIL/System/2.0.0.0__b77a5c561934e089/System.dll
----------------------------------------
System.Windows.Forms
    Assembly Version: 2.0.0.0
    Win32 Version: 2.0.50727.8784 (WinRel.050727-8700)
    CodeBase: file:///C:/WINDOWS/assembly/GAC_MSIL/System.Windows.Forms/2.0.0.0__b77a5c561934e089/System.Windows.Forms.dll
----------------------------------------
System.Drawing
    Assembly Version: 2.0.0.0
    Win32 Version: 2.0.50727.8784 (WinRel.050727-8700)
    CodeBase: file:///C:/WINDOWS/assembly/GAC_MSIL/System.Drawing/2.0.0.0__b03f5f7f11d50a3a/System.Drawing.dll
----------------------------------------
SlimDX
    Assembly Version: 2.0.13.43
    Win32 Version:
    CodeBase: file:///C:/WINDOWS/assembly/GAC_32/SlimDX/2.0.13.43__b1b0c32fd1ffe4f9/SlimDX.dll
----------------------------------------
msvcm90
    Assembly Version: 9.0.30729.9279
    Win32 Version: 9.00.30729.9279
    CodeBase: file:///C:/WINDOWS/WinSxS/x86_microsoft.vc90.crt_1fc8b3b9a1e18e3b_9.0.30729.9279_none_50939ec6bcb7c97c/msvcm90.dll
----------------------------------------
BuilderModes
    Assembly Version: 2.1.2.1553
    Win32 Version: 2.1.2.1553
    CodeBase: file:///D:/Programs/Doom%20Builder%202/Plugins/BuilderModes.dll
----------------------------------------
System.Design
    Assembly Version: 2.0.0.0
    Win32 Version: 2.0.50727.8784 (WinRel.050727-8700)
    CodeBase: file:///C:/WINDOWS/assembly/GAC_MSIL/System.Design/2.0.0.0__b03f5f7f11d50a3a/System.Design.dll
----------------------------------------
Sharpzip
    Assembly Version: 0.85.2.329
    Win32 Version: 0.85.2.329
    CodeBase: file:///D:/Programs/Doom%20Builder%202/Sharpzip.DLL
----------------------------------------
System.Xml
    Assembly Version: 2.0.0.0
    Win32 Version: 2.0.50727.8784 (WinRel.050727-8700)
    CodeBase: file:///C:/WINDOWS/assembly/GAC_MSIL/System.Xml/2.0.0.0__b77a5c561934e089/System.Xml.dll
----------------------------------------
TrackBar
    Assembly Version: 1.0.2486.37933
    Win32 Version: 1.0.2486.37933
    CodeBase: file:///D:/Programs/Doom%20Builder%202/TrackBar.DLL
----------------------------------------

************** JIT Debugging **************
To enable just-in-time (JIT) debugging, the .config file for this
application or computer (machine.config) must have the
jitDebugging value set in the system.windows.forms section.
The application must also be compiled with debugging
enabled.

For example:

<configuration>
    <system.windows.forms jitDebugging="true" />
</configuration>

When JIT debugging is enabled, any unhandled exception
will be sent to the JIT debugger registered on the computer
rather than be handled by this dialog box.