GHPerson#getType() should call populate() only if type is null

[anujhydrabadi]

Description

While calling the app or app installations endpoints, type is returned in the response from GitHub for users and organizations. Do not call populate() if type is already set. Perhaps we can fix this at the design level to prevent these kinds of bugs (caused because we do not know what fields have been populated already) from occurring altogether, but making a quick fix for this in the meantime.
Fixes #1816

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  • If this PR fixes one or more issues, include "Fixes #" lines for each issue.
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[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 83.54%. Comparing base (33c39f3) to head (ddbed20).

Files with missing lines	Patch %	Lines
src/main/java/org/kohsuke/github/GHPerson.java	0.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #2015      +/-   ##
============================================
- Coverage     83.61%   83.54%   -0.07%     
+ Complexity     2381     2379       -2     
============================================
  Files           235      235              
  Lines          7257     7258       +1     
  Branches        382      382              
============================================
- Hits           6068     6064       -4     
- Misses          955      957       +2     
- Partials        234      237       +3     

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