Merge pull request #1373 from adrian-prantl/64566000

Add a defensive nullptr check.

Author: adrian-prantl

lldb/source/Plugins/Language/Swift/SwiftOptional.cpp

@@ -221,7 +221,7 @@ lldb::ValueObjectSP lldb_private::formatters::swift::
   if (IsEmpty())
     return nullptr;
   auto child = m_some->GetChildAtIndex(idx, true);
-  if (m_some->IsSyntheticChildrenGenerated())
+  if (child && m_some->IsSyntheticChildrenGenerated())
     child->SetSyntheticChildrenGenerated(true);
   return child;
 }

lldb/test/API/lang/swift/variables/optionals/TestSwiftOptionals.py

@@ -102,4 +102,9 @@ def do_check_api(self):
             uoptString_Some,
             use_dynamic=False,
             num_children=1)
+        uoptString_Some.GetChildAtIndex(99)
 
+        # Querying a non-existing child should not crash.
+        synth_valobj = self.frame().FindVariable("optString_Some")
+        synth_valobj.SetSyntheticChildrenGenerated(True);
+        self.assertEqual(synth_valobj.GetChildAtIndex(1).GetSummary(), None)