Fix issue pasted image missing if no release permission (#16520)

* Fix issue pasted image missing if no release permission

* Update routers/web/web.go

Co-authored-by: zeripath <art27@cantab.net>

Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: 6543 <6543@obermui.de>

routers/web/web.go

@@ -827,9 +827,14 @@ func RegisterRoutes(m *web.Route) {
 			}
 			ctx.Data["CommitsCount"] = ctx.Repo.CommitsCount
 		})
-		m.Get("/attachments/{uuid}", repo.GetAttachment)
+
 	}, ignSignIn, context.RepoAssignment, context.UnitTypes(), reqRepoReleaseReader)
 
+	// to maintain compatibility with old attachments
+	m.Group("/{username}/{reponame}", func() {
+		m.Get("/attachments/{uuid}", repo.GetAttachment)
+	}, ignSignIn, context.RepoAssignment, context.UnitTypes())
+
 	m.Group("/{username}/{reponame}", func() {
 		m.Post("/topics", repo.TopicsPost)
 	}, context.RepoAssignment, context.RepoMustNotBeArchived(), reqRepoAdmin)