Empty strings in NO_PROXY sometimes treated as wildcard

[hpelwintervold]

Is this a support request?
No

Describe the bug
A clear and concise description of what the bug is.
NO_PROXY support added in #301 will treat empty strings as wildcards in some cases. The logic should only treat * as a wildcard, never empty string.

To reproduce
Set NO_PROXY to one of the below strings:
'secure.example.com:443,' (matches all addresses due to trailing ,)
:8080 (matches all hosts due to leading :)

Expected behavior
NO_PROXY parsing should be more defensive against empty strings encountered.
'secure.example.com:443,' should treat trailing ,as never matching anything, or an error:8080` should never match anything, or be an error

Logs
N/A

SDK version
9.6.0

Language version, developer tools
Python 3.12.2

OS/platform
Ubuntu

Additional context
Comparison of HTTP_PROXY/NO_PROXY implementations: https://about.gitlab.com/blog/2021/01/27/we-need-to-talk-no-proxy/

[keelerm84]

Fixed in v9.7.1