Unexpected behaviors when linking issues remotely

Summary

If a user has Link Issues permission in Jira instance A, but not in Jira instance B, he/she experiences unexpected behaviors when trying to link an issue from instance A to another one in instance B.

Steps to reproduce

1. Link 2 Jira instances together e.g. 1 Software instance and 1 SD instance
2. Ensure user A has accounts in both instances with the same username
3. Ensure user A is a developer that has Link Issues permission in Software, but is a customer that only has Portal access to the SD instance
4. As user A, open an issue in Software and attempt to link it to another issue in SD

Expected behavior

User A should be informed that he is not allowed to link issues to the SD instance

Actual behaviors

1. User A is not able to search for issues in SD. Jira throws a 500 error invisible to the user (can be seen from F12 devtools only):
   
2. If user A enters a valid issue key from SD and clicks Link, he/she gets an error page with this stacktrace:

   java.lang.NullPointerException
   	at net.oauth.signature.OAuthSignatureMethod.normalizeUrl(OAuthSignatureMethod.java:161) [?:?]
   	at net.oauth.signature.OAuthSignatureMethod.getBaseString(OAuthSignatureMethod.java:155) [?:?]
   	at net.oauth.signature.OAuthSignatureMethod.getSignature(OAuthSignatureMethod.java:81) [?:?]
   	at net.oauth.signature.OAuthSignatureMethod.sign(OAuthSignatureMethod.java:53) [?:?]
   

Notes

• If the applinks do not use Impersonation, user A is also asked to log in and approve, which will then take him/her to the Portal of the SD instance. He/she still cannot link issues.
• Sometimes clicking the arrow button on the Issue search box shows a history search of issues in the Software instance, which is not expected as the SD instance is being selected for issue linking.