In class AssociationWidget change member m_associationLine to value instead of pointer:

umbrello/umlwidgets/associationwidget.h
- Add #include "associationline.h".
- Remove forward declaraction of class AssociationLine.
- Replace accessor
    AssociationLine* associationLine() const
  by the two accessors
    const AssociationLine& associationLine() const;
    AssociationLine& associationLine().
- Omit pointer "*" at declaration of private member m_associationLine.

umbrello/umlwidgets/associationwidget.cpp
- Align code to the above changes. Functions affected:
  AssociationWidget(UMLScene*),
  create(UMLScene*, UMLWidget*, Uml::AssociationType::Enum, UMLWidget*),
  ~AssociationWidget, calculateNameTextSegment, operator=,
  associationLine, cleanup, isPointAddable, isPointRemovable,
  isAutoLayouted, setAssociationType, moveEvent, calculateEndingPoints,
  doUpdates, createPointsSelfAssociation, updatePointsSelfAssociation,
  createPointsException, updatePointsException, calculateTextPosition,
  constrainTextPos, computeAssocClassLine, mousePressEvent,
  mouseReleaseEvent, slotMenuSelection, setTextColor, setLineWidth,
  checkAddPoint, checkRemovePoint, checkAutoLayoutSpline,
  mouseMoveEvent, intersect, updateAssociations, updateRegionLineCount,
  setSelected, onAssociation, setXEntireAssoc, setYEntireAssoc,
  moveMidPointsBy, moveEntireAssoc, boundingRect, contextMenuEvent,
  hoverEnterEvent, hoverLeaveEvent, saveToXMI, loadFromXMI.
- In destructor remove call to cleanup().  Reason: cleanup() calls
  updateAssociations() which iterates over m_scene->associationList()
  which may in turn access association widgets that have already been
  deconstructed, resulting in crash.
- In function setUMLObject remove TODO comment about "It is not clear
  that we need associations to InstanceAttribute" and its attached code.
  Reason: InstanceAttribute is no longer a UMLClassifierListItem.
- Clean up documentation in functions calculateNameTextSegment,
  isPointAddable, isPointRemovable.
- In function linePathStartsAt remove TODO and activate its commented
  code such that it produces a local bool result1 as the result.
  Temporarily logical-OR result with result1 (subject to change).
- In function doUpdates declaration of `region' restore reference, i.e.
  change Uml::Region::Enum to Uml::Region::Enum&.  Reason: `region'
  shall act as a writable alias for m_role[role].m_WidgetRegion.
  The reference had been lost in commit bf937e26 (2013-07-26).

umbrello/dialogs/pages/umlwidgetstylepage.cpp
- Adjust functions init(), apply() to changed signature of
  AssociationWidget::associationLine().

umbrello/layoutgenerator.cpp
- Adjust function apply() to changed signature of
  AssociationWidget::associationLine().

umbrello/menus/associationwidgetpopupmenu.{h,cpp}
- Adjust function insertSubMenuLayout to changed signature of
  AssociationWidget::associationLine().

umbrello/toolbarstateassociation.cpp
- Adjust functions mouseReleaseAssociation, setSecondWidget to
  changed signature of AssociationWidget::associationLine().

umbrello/umlwidgets/classifierwidget.cpp
- Adjust function drawAsCircle to changed signature of
  AssociationWidget::associationLine().