[LLDB] Fix for regression of test 'TestDataFormatterInvalidStdUniquePtr.py' introduced in r374195

Differential Revision: https://reviews.llvm.org/D68641

llvm-svn: 374231
diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibStdcppTuple.cpp b/lldb/source/Plugins/Language/CPlusPlus/LibStdcppTuple.cpp
index 15bf7f8..0ac7b8f 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/LibStdcppTuple.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/LibStdcppTuple.cpp
@@ -90,7 +90,7 @@
 
 lldb::ValueObjectSP
 LibStdcppTupleSyntheticFrontEnd::GetChildAtIndex(size_t idx) {
-  if (idx < m_members.size())
+  if (idx < m_members.size() && m_members[idx])
     return m_members[idx]->GetSP();
   return lldb::ValueObjectSP();
 }