Always make sure main_div stretches to the bottom of the page.

If you narrow to a view that only has one or two message, sometimes
the grey box gets cut off and doesn't go to the bottom of the
page. This fixes that.

(imported from commit 55724d03aa30922d91bd33fab4447d889be78889)

zephyr/static/js/ui.js

@@ -134,6 +134,7 @@ function resizehandler(e) {
     }
 
     $("#bottom_whitespace").height($(window).height() * 0.4);
+    $("#main_div").css('min-height', viewport.height());
 
     // This function might run onReady (if we're in a narrow window),
     // but before we've loaded in the messages; in that case, don't