Fix CLI --actions="..." confused by trailing semicolon

This patch adds a check for an empty, or white space only, action. If the action is empty or white space only, we simply continue the loop.

The whitespace we account for is:

• space (0x20, ' ')
• form feed (0x0c, '\f')
• line feed (0x0a, '\n')
• carriage return (0x0d, '\r')
• horizontal tab (0x09, '\t')
• vertical tab (0x0b, '\v')

Fixes #3480 (closed)