Resolves: tdf#91542 crash on pressing return in sidebar line popup

Change-Id: I661a51f84827326dfc33a11a02f8065d68e8333a
(cherry picked from commit 2a6aa95a)

include/svx/sidebar/Popup.hxx

@@ -75,6 +75,8 @@ public :
     */
     void SetPopupModeEndHandler (const ::boost::function<void()>& rCallback);
 
+    void dispose();
+
 protected:
     VclPtr<PopupControl> mxControl;
 

svx/source/sidebar/line/LinePropertyPanel.cxx

@@ -213,6 +213,7 @@ void LinePropertyPanel::dispose()
     mpFTCapStyle.clear();
     mpLBCapStyle.clear();
 
+    maLineWidthPopup.dispose();
     maStyleControl.dispose();
     maDashControl.dispose();
     maWidthControl.dispose();

svx/source/sidebar/tools/Popup.cxx

@@ -40,12 +40,17 @@ Popup::Popup (
     OSL_ASSERT(maControlCreator);
 }
 
-Popup::~Popup()
+void Popup::dispose()
 {
     mxControl.disposeAndClear();
     mxContainer.disposeAndClear();
 }
 
+Popup::~Popup()
+{
+    dispose();
+}
+
 void Popup::Show (ToolBox& rToolBox)
 {
     rToolBox.SetItemDown(rToolBox.GetCurItemId(), true);