LP:680038 - bool close_thread_table(THD*, TABLE**): Assertion `table->key_read == 0' failed in EXPLAIN in maria-5.3-mwl89

Even after the fix for 609045, the following EXPLAIN query asserts as follows:

mysqld: sql_base.cc:1386: bool close_thread_table(THD*, TABLE**): Assertion `table->key_read == 0' failed.

#8 0x00133d98 in __assert_fail () from /lib/libc.so.6
#9 0x082e0ebf in close_thread_table (thd=0xb35e0e8, table_ptr=0xb35e134) at sql_base.cc:1386
#10 0x082e09d2 in close_open_tables (thd=0xb35e0e8) at sql_base.cc:1203
#11 0x082e0d6b in close_thread_tables (thd=0xb35e0e8) at sql_base.cc:1361
#12 0x0829308e in dispatch_command (command=COM_QUERY, thd=0xb35e0e8, packet=0xb376789 "", packet_length=405) at sql_parse.cc:1644
#13 0x08291376 in do_command (thd=0xb35e0e8) at sql_parse.cc:902
#14 0x0828e454 in handle_one_connection (arg=0xb35e0e8) at sql_connect.cc:1154
#15 0x00bea919 in start_thread () from /lib/libpthread.so.0
#16 0x001edcbe in clone () from /lib/libc.so.6