[lldb] Fix crash in FormatEntity for mangled-name

[kastiglione]

Summary

Check a Block pointer before dereferencing.

Using function.mangled-name led to a crash for a frame where the symbol
context had no block info. In my case, the frame's function was a system frame.

[mib]

LGTM! Thanks for catching that!

lldb/source/Core/FormatEntity.cpp

else if (sc->function)
       name = sc->function->GetMangled()
                  .GetName(Mangled::ePreferMangled)
                  .AsCString();
 
     if (!name)
       return false;
     s.PutCString(name);
 
-    if (sc->block->GetContainingInlinedBlock()) {
+    if (sc->block && sc->block->GetContainingInlinedBlock()) {
       if (const InlineFunctionInfo *inline_info =
               sc->block->GetInlinedFunctionInfo()) {
         s.PutCString(" [inlined] ");
         inline_info->GetName().Dump(&s);
       }
     }
     return true;
   }