fix bug: if regex.search(value): TypeError: expected string or bytes…

[sunwenquan]

Fix the following exception information.

"/Users/gavinsun/Research/Django/19.beautiful_app/django_app/user_sessions/templatetags/user_sessions.py", line 58, in device
    if regex.search(value):
TypeError: expected string or bytes-like object
[05/Jul/2018 15:52:06] "GET /account/sessions/ HTTP/1.1" 500 191771

Description

In user_sessions/templatetags/user_sessions.py,line 58，when value is None, python throws an exception. I added the following code in front to solve this problem.

    if not value:
        return None

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codecov]

Codecov Report

Merging #87 into master will increase coverage by 0.04%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #87      +/-   ##
==========================================
+ Coverage   93.84%   93.88%   +0.04%     
==========================================
  Files          10       10              
  Lines         276      278       +2     
  Branches       31       32       +1     
==========================================
+ Hits          259      261       +2     
  Misses         11       11              
  Partials        6        6

Impacted Files	Coverage Δ
user_sessions/templatetags/user_sessions.py	94.23% <100%> (+0.23%)	⬆️

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[Bouke]

Can you explain why this change is needed? What caused user_agent to be None in the first place?

[sunwenquan]

When I visited http://localhost:8000/account/sessions/

For example

1. Run the django app https://github.com/sunwenquan/django-app-test.git
2. Visited http://localhost:8000/account/sessions/

[Bouke]

That's not normal behaviour. Please investigate why the usage agent has not been set for that user. This could be caused by another issue altogether.

[SchrodingersGat]

@Bouke to raise this issue from the dead, I have found that this issue can arise when using the django testing framework to render a page - the user agent is not necessarily set

e.g.

def some_test(self):
    self.client.get("/page/")

leads to

![image](https://user-images.githubusercontent.com/10080325/181153596-242cc577-ce0b-4910-9beb-b4243561b411.png)