fix a warning in display.c

display.c: In function ‘redraw_map’:
display.c:1460:15: warning: variable ‘glyph’ set but not used [-Wunused-but-set-variable]
 1460 |     int x, y, glyph;
      |               ^~~~~

src/display.c

@@ -1484,6 +1484,9 @@ redraw_map()
                         Glyphinfo_at(x, y, glyph), &bkglyphinfo);
         }
     flush_screen(1);
+#ifndef UNBUFFERED_GLYPHINFO
+    nhUse(glyph);
+#endif
 }
 
 /*