Execute the following:

1. CREATE TABLE foo(event Date, bar Array(FixedString(16))) ENGINE = MergeTree(event, (event), 8192);
2. INSERT INTO foo(event, bar) VALUES(now(), array(toFixedString('a', 16)))
3. SELECT notEmpty(bar) ? arrayJoin(bar) : toFixedString('', 16) FROM foo

Execution of select results in server-side exception:
executeQuery: Code: 368, e.displayText() = DB::Exception: Bad cast from type N2DB12ColumnStringE to N2DB17ColumnFixedStringE, e.what() = DB::Exception (from 172.17.0.2:59670) (in query: SELECT notEmpty(bar) ? arrayJoin(bar) : toFixedString('', 16) FROM foo), Stack trace:

0. /usr/bin/clickhouse-server(StackTrace::StackTrace()+0x16) [0x29b2626]
1. /usr/bin/clickhouse-server(DB::Exception::Exception(std::__cxx11::basic_string<char, std::char_traits, std::allocator > const&, int)+0x1f) [0x10b079f]
2. /usr/bin/clickhouse-server(std::enable_if<std::is_referenceDB::ColumnFixedString&::value, DB::ColumnFixedString&>::type typeid_cast<DB::ColumnFixedString&, DB::IColumn>(DB::IColumn&)+0xef) [0x1bab39f]
3. /usr/bin/clickhouse-server(DB::DataTypeFixedString::serializeBinaryBulk(DB::IColumn const&, DB::WriteBuffer&, unsigned long, unsigned long) const+0x25) [0x237f355]
4. /usr/bin/clickhouse-server(DB::NativeBlockOutputStream::writeData(DB::IDataType const&, std::shared_ptrDB::IColumn const&, DB::WriteBuffer&, unsigned long, unsigned long)+0x2d4) [0x23549c4]
5. /usr/bin/clickhouse-server(DB::NativeBlockOutputStream::write(DB::Block const&)+0xd60) [0x2355950]
6. /usr/bin/clickhouse-server(DB::TCPHandler::sendData(DB::Block&)+0x52) [0x10c83c2]
7. /usr/bin/clickhouse-server(DB::TCPHandler::processOrdinaryQuery()+0x46f) [0x10c885f]
8. /usr/bin/clickhouse-server(DB::TCPHandler::runImpl()+0x7c5) [0x10ca505]
9. /usr/bin/clickhouse-server(DB::TCPHandler::run()+0x2b) [0x10caf6b]
10. /usr/bin/clickhouse-server(Poco::Net::TCPServerConnection::start()+0xf) [0x32b47af]
11. /usr/bin/clickhouse-server(Poco::Net::TCPServerDispatcher::run()+0x13b) [0x32babeb]
12. /usr/bin/clickhouse-server(Poco::PooledThread::run()+0xb7) [0x3525be7]
13. /usr/bin/clickhouse-server(Poco::ThreadImpl::runnableEntry(void*)+0xa5) [0x34f1c25]
14. /lib/x86_64-linux-gnu/libpthread.so.0(+0x76ba) [0x7f1c47bf96ba]
15. /lib/x86_64-linux-gnu/libc.so.6(clone+0x6d) [0x7f1c4721a3dd]

and in client-side exception:
Exception on client:
Code: 89. DB::Exception: Unknown compression method: 105: while receiving packet from clickhouse-server:9000, 172.17.0.3

If you format output as JSON, it produces fields description correctly but fails on data in the same way.

Version of both client and server is 1.1.54245