xmloff: fix leak in XMLPropertySetMapperEntry_Impl

The XMLNamedBoolPropertyHdl should be owned by
OControlPropertyHandlerFactory like all the other handlers created in
that function.

Thanks to Julien Nabet for pointing out the problem.

Change-Id: Id474b2fdb84ca74f686d0c888fbedbee623c31bb
Reviewed-on: https://gerrit.libreoffice.org/52666Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Michael Stahl <Michael.Stahl@cib.de>

include/xmloff/controlpropertyhdl.hxx

@@ -30,6 +30,7 @@
 #include <rtl/ustring.hxx>
 #include <xmloff/xmlexppr.hxx>
 #include <xmloff/XMLConstantsPropertyHandler.hxx>
+#include <xmloff/NamedBoolPropertyHdl.hxx>
 
 template<typename EnumT> struct SvXMLEnumMapEntry;
 class Color;
@@ -119,6 +120,7 @@ namespace xmloff
         mutable std::unique_ptr<OFontWidthHandler>              m_pFontWidthHandler;
         mutable std::unique_ptr<XMLConstantsPropertyHandler>    m_pFontEmphasisHandler;
         mutable std::unique_ptr<XMLConstantsPropertyHandler>    m_pFontReliefHandler;
+        mutable std::unique_ptr<XMLNamedBoolPropertyHdl>        m_pTextLineModeHandler;
 
     public:
         OControlPropertyHandlerFactory();

xmloff/source/forms/controlpropertyhdl.cxx

@@ -99,9 +99,13 @@ namespace xmloff
                 pHandler = m_pFontReliefHandler.get();
                 break;
             case XML_TYPE_TEXT_LINE_MODE:
-                pHandler = new XMLNamedBoolPropertyHdl(
-                                            ::xmloff::token::XML_SKIP_WHITE_SPACE,
-                                            ::xmloff::token::XML_CONTINUOUS);
+                if (!m_pTextLineModeHandler)
+                {
+                    m_pTextLineModeHandler = o3tl::make_unique<XMLNamedBoolPropertyHdl>(
+                            ::xmloff::token::XML_SKIP_WHITE_SPACE,
+                            ::xmloff::token::XML_CONTINUOUS);
+                }
+                pHandler = m_pTextLineModeHandler.get();
                 break;
         }