fix: document that /repos/{owner}/{repo}/pulls may contain nulls (#7762)

The null means a server side bug prevents the pull request from being
retrieved.

Closes https://codeberg.org/forgejo/forgejo/issues/6571

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/7762
Reviewed-by: Michael Kriese <michael.kriese@gmx.de>
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Co-authored-by: Earl Warren <contact@earl-warren.org>
Co-committed-by: Earl Warren <contact@earl-warren.org>

routers/api/v1/repo/pull.go

@@ -47,7 +47,7 @@ import (
 func ListPullRequests(ctx *context.APIContext) {
 	// swagger:operation GET /repos/{owner}/{repo}/pulls repository repoListPullRequests
 	// ---
-	// summary: List a repo's pull requests
+	// summary: List a repo's pull requests. If a pull request is selected but fails to be retrieved for any reason, it will be a null value in the list of results.
 	// produces:
 	// - application/json
 	// parameters:

templates/swagger/v1_json.tmpl

@@ -12767,7 +12767,7 @@
         "tags": [
           "repository"
         ],
-        "summary": "List a repo's pull requests",
+        "summary": "List a repo's pull requests. If a pull request is selected but fails to be retrieved for any reason, it will be a null value in the list of results.",
         "operationId": "repoListPullRequests",
         "parameters": [
           {