fix: Retry if there is no git auth user yet (#5316)

Fixes part of #4900.

coderd/workspaceagents.go

@@ -1154,6 +1154,9 @@ func (api *API) workspaceAgentsGitAuth(rw http.ResponseWriter, r *http.Request)
 				UserID:     workspace.OwnerID,
 			})
 			if err != nil {
+				if errors.Is(err, sql.ErrNoRows) {
+					continue
+				}
 				httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
 					Message: "Failed to get git auth link.",
 					Detail:  err.Error(),