fix: check if there is an email field in userinfo

[chakku000]

Description

When using OAuth authorization provider which doesn't give email information, oauth_authorized method cause KeyError exception. This is because at Line714, userinfo's email key is accessed even if userinfo does not have email key.

ADDITIONAL INFORMATION

• Has associated issue:
• Is CRUD MVC related.
• Is Auth, RBAC security related.
• Changes the security db schema.
• Introduces new feature
• Removes existing feature

[codecov]

Codecov Report

Merging #1663 (fa19984) into master (f0608fb) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##           master    #1663   +/-   ##
=======================================
  Coverage   76.43%   76.43%           
=======================================
  Files          55       55           
  Lines        8032     8032           
=======================================
  Hits         6139     6139           
  Misses       1893     1893           

Flag	Coverage Δ
python	76.43% <0.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
flask_appbuilder/security/views.py	61.74% <0.00%> (ø)

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[dpgaspar]

Thank you for the fix