Clear the register context if our process is no longer alive.

llvm-svn: 180927

lldb/source/Plugins/Process/Utility/RegisterContextThreadMemory.cpp

@@ -63,6 +63,10 @@ RegisterContextThreadMemory::UpdateRegisterContext ()
                 }                
             }
         }
+        else
+        {
+            m_reg_ctx_sp.reset();
+        }
     }
     else
     {