Sync management thread panicked at every entry in by_parent.values() has corresponding entry in by_hash.keys()

[5chdn]

Running the uahf branch (but probably not related) in verification mode none.

2017-08-18 14:06:46  INFO sync "14:06:46" Processed 0 blocks in 60.08 seconds. Peers: [active:7, idle:0, bad:3]. Chain: [sch:19025 -> req:523 -> vfy:0 -> stored: 396830]
2017-08-18 14:07:47  INFO sync "14:07:47" Processed 0 blocks in 60.91 seconds. Peers: [active:8, idle:0, bad:2]. Chain: [sch:21009 -> req:458 -> vfy:0 -> stored: 396830]
2017-08-18 14:08:48  INFO sync "14:08:48" Processed 0 blocks in 61.27 seconds. Peers: [active:8, idle:0, bad:2]. Chain: [sch:20945 -> req:483 -> vfy:0 -> stored: 396830]
2017-08-18 14:08:50  WARN sync Failed to get requested block from peer#76 in 24.759691744999145 seconds
thread 'Sync management thread' panicked at 'every entry in by_parent.values() has corresponding entry in by_hash.keys()', /checkout/src/libcore/option.rs:819:4
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
stack backtrace:
   0: std::sys::imp::backtrace::tracing::imp::unwind_backtrace
             at /checkout/src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::_print
             at /checkout/src/libstd/sys_common/backtrace.rs:71
   2: std::panicking::default_hook::{{closure}}
             at /checkout/src/libstd/sys_common/backtrace.rs:60
             at /checkout/src/libstd/panicking.rs:380
   3: std::panicking::default_hook
             at /checkout/src/libstd/panicking.rs:396
   4: std::panicking::rust_panic_with_hook
             at /checkout/src/libstd/panicking.rs:611
   5: std::panicking::begin_panic_new
             at /checkout/src/libstd/panicking.rs:553
   6: std::panicking::begin_panic_fmt
             at /checkout/src/libstd/panicking.rs:521
   7: rust_begin_unwind
             at /checkout/src/libstd/panicking.rs:497
   8: core::panicking::panic_fmt
             at /checkout/src/libcore/panicking.rs:92
   9: core::option::expect_failed
             at /checkout/src/libcore/option.rs:819
  10: sync::utils::orphan_transactions_pool::OrphanTransactionsPool::remove_transactions_for_parent
             at /checkout/src/libcore/option.rs:302
             at sync/src/utils/orphan_transactions_pool.rs:83
  11: sync::utils::orphan_transactions_pool::OrphanTransactionsPool::remove_transactions
             at sync/src/utils/orphan_transactions_pool.rs:110
  12: sync::synchronization_manager::manage_orphaned_transactions
             at sync/src/synchronization_manager.rs:302
Aborted (core dumped)