Fix memory leak in FileDialogHelper_Impl::createMatcher/addFilters.

Before resetting mpMatcher to a new value check whether the current
value needs to be deleted first.

Change-Id: I26039c19483621d809dbd8474b86254948efc9f6
Reviewed-on: https://gerrit.libreoffice.org/4194Reviewed-by: David Tardon <dtardon@redhat.com>
Tested-by: David Tardon <dtardon@redhat.com>

sfx2/source/dialog/filedlghelper.cxx

@@ -1769,6 +1769,9 @@ void FileDialogHelper_Impl::setFilter( const OUString& rFilter )
 // ------------------------------------------------------------------------
 void FileDialogHelper_Impl::createMatcher( const String& rFactory )
 {
+    if (mbDeleteMatcher)
+        delete mpMatcher;
+
     mpMatcher = new SfxFilterMatcher( SfxObjectShell::GetServiceNameFromFactory(rFactory) );
     mbDeleteMatcher = sal_True;
 }
@@ -1783,6 +1786,9 @@ void FileDialogHelper_Impl::addFilters( const String& rFactory,
     if ( ! xFltMgr.is() )
         return;
 
+    if (mbDeleteMatcher)
+        delete mpMatcher;
+
     // we still need a matcher to convert UI names to filter names
     if ( !rFactory.Len() )
     {