Fix SalLayoutGlyphs copy constructor

Since we can't know the real SalLayoutGlyphsImpl type, we
always have to clone and delete it on assignemt and in the
copy constructor.

Change-Id: I3e3aa1e0271c5ecbb1474a70fae5e63bd7124677
Reviewed-on: https://gerrit.libreoffice.org/62583
Tested-by: Jenkins
Reviewed-by: Jan-Marek Glogowski <glogow@fbihome.de>

vcl/source/gdi/impglyphitem.cxx

@@ -26,14 +26,12 @@ SalLayoutGlyphs::SalLayoutGlyphs()
 
 SalLayoutGlyphs::~SalLayoutGlyphs() { delete m_pImpl; }
 
-SalLayoutGlyphs::SalLayoutGlyphs(const SalLayoutGlyphs& rOther) { *m_pImpl = *rOther.m_pImpl; }
+SalLayoutGlyphs::SalLayoutGlyphs(const SalLayoutGlyphs& rOther) { operator=(rOther); }
 
 SalLayoutGlyphs& SalLayoutGlyphs::operator=(const SalLayoutGlyphs& rOther)
 {
-    if (m_pImpl)
-        *m_pImpl = *rOther.m_pImpl;
-    else
-        m_pImpl = rOther.m_pImpl->clone(*this);
+    delete m_pImpl;
+    m_pImpl = rOther.m_pImpl ? rOther.m_pImpl->clone(*this) : nullptr;
     return *this;
 }