Loading as session file leads to broken UI if a log file in session is not found

[AndisGrossteins]

When loading a session file (*.lxj), if any of the log files saved in session are not not accessible, LogExpert creates an empty LogWindow that is detached from the main application window for each missing file. The detached windows don't have title bar, don't appear in the task bar, but can be closed using Alt+F4.

Steps to reproduce:

1. Create a session file test_session.lxj with non-existent files in the FileNames:

{
  "FileNames": [
	"non-existent-file.log",
	"another-file.log"
  ],
  "TabLayoutXml": "<!--DockPanel configuration file. Author: Weifen Luo, all rights reserved.-->\r\n<!--!!! AUTOMATICALLY GENERATED FILE. DO NOT MODIFY !!!-->\r\n<DockPanel FormatVersion=\"1.0\" DockLeftPortion=\"0.25\" DockRightPortion=\"0.25\" DockTopPortion=\"0.25\" DockBottomPortion=\"0.25\" ActiveDocumentPane=\"-1\" ActivePane=\"-1\">\r\n  <Contents Count=\"0\" />\r\n  <Panes Count=\"0\" />\r\n  <DockWindows>\r\n    <DockWindow ID=\"0\" DockState=\"Document\" ZOrderIndex=\"1\">\r\n      <NestedPanes Count=\"0\" />\r\n    </DockWindow>\r\n    <DockWindow ID=\"1\" DockState=\"DockLeft\" ZOrderIndex=\"4\">\r\n      <NestedPanes Count=\"0\" />\r\n    </DockWindow>\r\n    <DockWindow ID=\"2\" DockState=\"DockRight\" ZOrderIndex=\"5\">\r\n      <NestedPanes Count=\"0\" />\r\n    </DockWindow>\r\n    <DockWindow ID=\"3\" DockState=\"DockTop\" ZOrderIndex=\"6\">\r\n      <NestedPanes Count=\"0\" />\r\n    </DockWindow>\r\n    <DockWindow ID=\"4\" DockState=\"DockBottom\" ZOrderIndex=\"7\">\r\n      <NestedPanes Count=\"0\" />\r\n    </DockWindow>\r\n  </DockWindows>\r\n  <FloatWindows Count=\"0\" />\r\n</DockPanel>"
}

2. Load the session file using File > Load Session...

No errors or warning about missing files are displayed and the UI is left in a broken state.

[Hirogen]

I think the dockpanel config is broken, probably due to the escaped characters