Fix NPE when editing OAuth2 applications (go-gitea#27078)

Fixes go-gitea#27072

It looks like there are some cases where `ContextUser` is not set here

---------

Co-authored-by: techknowlogick <[email protected]>

Author: JakobDev

routers/web/user/setting/oauth2_common.go

@@ -27,9 +27,8 @@ func (oa *OAuth2CommonHandlers) renderEditPage(ctx *context.Context) {
 	app := ctx.Data["App"].(*auth.OAuth2Application)
 	ctx.Data["FormActionPath"] = fmt.Sprintf("%s/%d", oa.BasePathEditPrefix, app.ID)
 
-	if ctx.ContextUser.IsOrganization() {
-		err := shared_user.LoadHeaderCount(ctx)
-		if err != nil {
+	if ctx.ContextUser != nil && ctx.ContextUser.IsOrganization() {
+		if err := shared_user.LoadHeaderCount(ctx); err != nil {
 			ctx.ServerError("LoadHeaderCount", err)
 			return
 		}
@@ -68,6 +67,7 @@ func (oa *OAuth2CommonHandlers) AddApp(ctx *context.Context) {
 		ctx.ServerError("GenerateClientSecret", err)
 		return
 	}
+
 	oa.renderEditPage(ctx)
 }