Fix issue generation failing after deleting a PR (#42001)

Seems that #41416 PR has been somehow (?) deleted and when we try
to generate issue links for it, the issue generation fails (and it
is not an issue as well). This change should workaround that by
skipping the PR.

dev/breeze/src/airflow_breeze/commands/release_management_commands.py

@@ -2093,7 +2093,7 @@ class ProviderPRInfo(NamedTuple):
                     except UnknownObjectException:
                         get_console().print(f"[red]The PR #{pr_number} could not be found[/]")
                 # Retrieve linked issues
-                if pull_requests[pr_number].body:
+                if pr_number in pull_requests and pull_requests[pr_number].body:
                     body = " ".join(pull_requests[pr_number].body.splitlines())
                     linked_issue_numbers = {
                         int(issue_match.group(1)) for issue_match in ISSUE_MATCH_IN_BODY.finditer(body)