svx: fix Writer's insert -> frame crash

(regression from 6e61ecd0)

Change-Id: Ifd8d482031b7fce4341d488f7276620e52f549ed

svx/source/dialog/dlgctrl.cxx

@@ -1389,7 +1389,7 @@ void GradientLB::Modify( const XGradientEntry& rEntry, sal_Int32 nPos, const Bit
 void GradientLB::SelectEntryByList( const XGradientListRef &pList, const OUString& rStr,
                                     const XGradient& rGradient, sal_uInt16 nDist )
 {
-    long nCount = pList->Count();
+    long nCount = pList.get() ? pList->Count() : 0;
     XGradientEntry* pEntry;
     bool bFound = false;
     OUString aStr;