Fixed SEGV caused by dereferencing NULL pointer when right clicking

inside files not supported. This relates to bug 3173.

Signed-off-by: Michele Calgaro <michele.calgaro@yahoo.it>
(cherry picked from commit 8db2223147)

languages/cpp/cppsupportpart.cpp

@@ -1734,7 +1734,12 @@ void CppSupportPart::MakeMemberHelper( TQString& text, int& atLine, int& atColum
 	TQString implFile = findSourceFile();
 
 	m_backgroundParser->lock();
-	TranslationUnitAST* translationUnit = *m_backgroundParser->translationUnit( m_activeFileName );
+	ParsedFilePointer pTranslationUnit = m_backgroundParser->translationUnit( m_activeFileName );
+	TranslationUnitAST *translationUnit = NULL;
+	if (pTranslationUnit)
+	{
+		translationUnit = *pTranslationUnit;
+	}
 	if ( translationUnit )
 	{
 		bool fail = false;