gtk+'s configure.ac  m4_define([pango_required_version], [1.20])

when using pango less than 1.22.4. the following programs print a warning message:
----------------------------
#include <gtk/gtk.h>

int main(int argc, char *argv[])
{
  GtkWidget *window;
  GtkWidget *entry;

  gtk_init (&argc, &argv);

  window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
  
  entry = gtk_entry_new ();

  gtk_container_add (GTK_CONTAINER(window), entry);

  gtk_widget_show_all (window);

  gtk_main ();

  return 0;
}
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I read gtk+ source code, just find gtk_entry_get_preferred_width call gtk_style_context_get_font. But gtk_style_context_get_font return NULL.
And pango less then 1.22.4, pango_context_get_metrics not allow desc is NULL.

fix gtk_style_context_get_font or fix gtk+'s configure.ac?