fix(intro): still show intro message with floating window

Stop drawing the intro only after a split is opened.

src/nvim/version.c

@@ -34,6 +34,7 @@
 #include "nvim/strings.h"
 #include "nvim/ui.h"
 #include "nvim/version.h"
+#include "nvim/window.h"
 
 // for ":version", ":intro", and "nvim --version"
 #ifndef NVIM_VERSION_MEDIUM
@@ -2714,9 +2715,9 @@ void list_version(void)
 /// Whether it still is not too late to show an intro message
 bool may_show_intro(void)
 {
-  return (buf_is_empty(curbuf)
-          && (curbuf->b_fname == NULL)
-          && (firstwin->w_next == NULL)
+  return (buf_is_empty(firstwin->w_buffer)
+          && (firstwin->w_buffer->b_fname == NULL)
+          && one_window(firstwin)
           && (vim_strchr(p_shm, SHM_INTRO) == NULL));
 }