If the shell history file does not contain a timestamps for the lines
osquery will miss the time in rows and will show an confusing error
about attempt to convert empty string to INTEGER.
```
% head -n 3 ~/.zsh_history
ls
cd source
ls
```
```
osquery> select * from shell_history limit 1;
I0621 11:56:37.804193 2629124992 virtual_table.cpp:292] Error casting time () to INTEGER
+------------+------+---------+-------------------------------+
| uid | time | command | history_file |
+------------+------+---------+-------------------------------+
| 1868255265 | | exit | /home/akindyakov/.zsh_history |
+------------+------+---------+-------------------------------+
```
So, default value for the time in shell history can solve the problem.
