Resolves: tdf#120334 crash on ESC in position and size

Change-Id: I50421f01ca368ec4d074db4b0add2f08b7b3fc0d
Reviewed-on: https://gerrit.libreoffice.org/61448
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

cui/source/inc/swpossizetabpage.hxx

@@ -113,6 +113,7 @@ class SvxSwPosSizeTabPage : public SfxTabPage
 
 public:
     SvxSwPosSizeTabPage(TabPageParent pParent, const SfxItemSet& rInAttrs);
+    virtual void dispose() override;
     virtual ~SvxSwPosSizeTabPage() override;
 
     static VclPtr<SfxTabPage> Create( TabPageParent, const SfxItemSet* );

cui/source/tabpages/swpossizetabpage.cxx

@@ -595,6 +595,16 @@ SvxSwPosSizeTabPage::SvxSwPosSizeTabPage(TabPageParent pParent, const SfxItemSet
 
 SvxSwPosSizeTabPage::~SvxSwPosSizeTabPage()
 {
+    disposeOnce();
+}
+
+void SvxSwPosSizeTabPage::dispose()
+{
+    m_xWidthMF.reset();
+    m_xHeightMF.reset();
+    m_xHoriByMF.reset();
+    m_xVertByMF.reset();
+    SfxTabPage::dispose();
 }
 
 namespace