fix: prevent panic when processing null project items

The GraphQL API can return `null` nodes in the `projectItems`
connection, causing a runtime panic (nil pointer dereference) when the
CLI attempted to access fields on these nil nodes. This crash occurs
even with personal access tokens with full read access.

Adds a check to safely skip `nil` nodes in `ProjectsV2ItemsForIssue` and
`ProjectsV2ItemsForPullRequest`.

Signed-off-by: Chris Henzie <chrishenzie@google.com>

Author: chrishenzie

api/queries_projects_v2.go

@@ -106,6 +106,9 @@ func ProjectsV2ItemsForIssue(client *Client, repo ghrepo.Interface, issue *Issue
 			return err
 		}
 		for _, projectItemNode := range query.Repository.Issue.ProjectItems.Nodes {
+			if projectItemNode == nil {
+				continue
+			}
 			items.Nodes = append(items.Nodes, &ProjectV2Item{
 				ID: projectItemNode.ID,
 				Project: ProjectV2ItemProject{
@@ -175,6 +178,9 @@ func ProjectsV2ItemsForPullRequest(client *Client, repo ghrepo.Interface, pr *Pu
 		}
 
 		for _, projectItemNode := range query.Repository.PullRequest.ProjectItems.Nodes {
+			if projectItemNode == nil {
+				continue
+			}
 			items.Nodes = append(items.Nodes, &ProjectV2Item{
 				ID: projectItemNode.ID,
 				Project: ProjectV2ItemProject{