do not attempt to redo past the last available operation

src/core/Buffer.cc

@@ -409,7 +409,7 @@ void Buffer::redo()
             child_index = 0u;
         }
     }
-    else
+    else if (m_change_operations[m_current_change_operation_index]->children.size() > 0u)
     {
         child_index = *m_change_operations[m_current_change_operation_index]->children.begin();
     }