[BUG] Crash on open for Ubuntu 16

[UltimateBrent]

Describe the bug
Logged into a few of our AWS Ubuntu 16 machines, and they would render the frames, then it would crash. If it's not supported, this should help you figure compatibility to list in the README.

Info (please complete the following information):

• Ubuntu 16.04.6 LTS (GNU/Linux 4.4.0-1044-aws x86_64)
• Lang: en_US.UTF-8
• Bash version: GNU bash, version 4.3.48(1)-release (x86_64-pc-linux-gnu)

Additional context
$HOME/.config/bashtop/error.log"

New instance of bashtop version: 0.8.3 Pid: 18459
04:49:12 AM ERROR: On line 724 
04:49:12 AM ERROR: On line 724 (MUTED!)
./bashtop: line 669: /sys/devices/system/cpu/cpu-1/cpufreq/scaling_cur_freq: No such file or directory
04:49:12 AM ERROR: On line 669 
04:49:12 AM ERROR: On line 682 
04:49:12 AM ERROR: On line 724 
04:49:12 AM ERROR: On line 724 (MUTED!)
./bashtop: line 1412: mem[available]*100/mem[total]: division by 0 (error token is "mem[total]")
error: improper AIX field descriptor

Usage:
 ps [options]

 Try 'ps --help <simple|list|output|threads|misc|all>'
  or 'ps --help <s|l|o|t|m|a>'
 for additional help text.

For more details see ps(1).
04:49:12 AM ERROR: On line 1503 
./bashtop: line 669: /sys/devices/system/cpu/cpu-1/cpufreq/scaling_cur_freq: No such file or directory
04:49:12 AM ERROR: On line 669 
04:49:12 AM ERROR: On line 682 
./bashtop: line 914: local: `': not a valid identifier
04:49:12 AM ERROR: On line 914 
./bashtop: line 914: local: `': not a valid identifier
04:49:12 AM ERROR: On line 914 (MUTED!)
./bashtop: line 914: local: `': not a valid identifier
./bashtop: line 914: local: `': not a valid identifier
error: improper AIX field descriptor

Usage:
 ps [options]

 Try 'ps --help <simple|list|output|threads|misc|all>'
  or 'ps --help <s|l|o|t|m|a>'
 for additional help text.

For more details see ps(1).
04:49:14 AM ERROR: On line 1503 
./bashtop: line 669: /sys/devices/system/cpu/cpu-1/cpufreq/scaling_cur_freq: No such file or directory
04:49:15 AM ERROR: On line 669 
04:49:15 AM ERROR: On line 682 
04:49:15 AM ERROR: On line 939 
04:49:15 AM ERROR: On line 939 (MUTED!)
./bashtop: line 1743: (Receive-Receive)*1000/(net[new_timestamp]-net[old_timestamp]) : division by 0 (error token is "(net[new_timestamp]-net[old_timestamp]) ")

[aristocratos]

Bash version is below listed minimum version in dependencies:

bash (v4.4 or later)

Looking at the error.log there are indications of errors from output of "ps". Could be a version incompatibility there too, but if so, it will be fixed in the next big update where python psutil will be used instead.

So are not going to look into this any deeper right now unless you update bash and get the same errors.