I have observed a very similar error when trying to open any existing .xmi files containing UML documents, which I created using Umbrello a few months ago (probably on an early version).
Here is the output from a command-line invocation: umbrello: too big indentation amount = 1937010287 Shortcut for action "delete_selected" "Delete &Selected" set with QAction::setShortcut()! Use KActionCollection::setDefaultShortcut(s) instead. Shortcut for action "move_tab_left" "&Move Tab Left" set with QAction::setShortcut()! Use KActionCollection::setDefaultShortcut(s) instead. Shortcut for action "move_tab_right" "&Move Tab Right" set with QAction::setShortcut()! Use KActionCollection::setDefaultShortcut(s) instead. Shortcut for action "previous_tab" "Select Diagram on Left" set with QAction::setShortcut()! Use KActionCollection::setDefaultShortcut(s) instead. Shortcut for action "next_tab" "Select Diagram on Right" set with QAction::setShortcut()! Use KActionCollection::setDefaultShortcut(s) instead. Illegal icon group: 7 umbrello: view is NULL umbrello: "folder" : umlPackage not set on object umbrello: UMLDoc::openDocument: copy from QUrl("file:Figures_11.xmi") to QUrl("file:///tmp/umbrello.M21206") . klauncher not running... launching kdeinit klauncher not running... launching kdeinit klauncher not running... launching kdeinit couldn't create slave: "Cannot talk to klauncher: The name org.kde.klauncher5 was not provided by any .service files" umbrello: UMLDoc::openDocument: "Could not start process Cannot talk to klauncher: The name org.kde.klauncher5 was not provided by any .service files." umbrello: view is NULL umbrello: "folder" : umlPackage not set on object -- Murray J Brown