fix gee coefficient display (#695)

close #694

<!--- Replace `#nnn` with your issue link for reference. -->

Fixes #nnn

Signed-off-by: Joe Zhu <sha.joe.zhu@gmail.com>
Co-authored-by: Emily de la Rua <59304861+edelarua@users.noreply.github.com>

R/tm_a_gee.R

@@ -76,7 +76,7 @@ template_a_gee <- function(output_table,
       } else if (output_table == "t_gee_coef") {
         substitute(
           expr = {
-            result_table <- tern.gee::as.rtable(model_fit, type = "coef", conf_level = conf_level)
+            result_table <- tern.gee::as.rtable(data.frame(Coefficient = model_fit$coefficients))
             subtitles(result_table) <- st
             main_footer(result_table) <- mf
           },