IDA plugin: Fix SIGSEGV in CallGraph::IsLibrary when viewing flow graphs When diff results are loaded from disk (is_incomplete() == true), Results::PrepareVisualDiff was experiencing a segmentation fault: 1. primary and secondary std::unique_ptr<FlowGraph> were declared inside the if (is_incomplete()) block, causing them to be destroyed prior to database writing. Their destructor detached them from the call graph and set call_graph_ to null. 2. database_writer->Write was passed member variables flow_graphs1_, flow_graphs2_, and fixed_points_ instead of the local variables containing only the selected function pair. Extend the lifetime of primary and secondary across PrepareVisualDiff and pass the local flow_graphs1, flow_graphs2, and fixed_points to database_writer->Write. PiperOrigin-RevId: 977992480 Change-Id: I35d4867cb6c76b30a3d9e94ec89ae6a9d2056821