Dialog: Fixed the case where you open two modal dialogs and then clos…

…e the top dialog and inputs in the first dialog were no longer usable - Fixes #4309.

ui/ui.dialog.js

@@ -172,6 +172,17 @@ $.widget("ui.dialog", {
 		$.ui.dialog.overlay.resize();
 
 		self._isOpen = false;
+
+		// adjust the maxZ to allow other modal dialogs to continue to work (see #4309)
+		if (self.options.modal) {
+			var maxZ = 0;
+			$('.ui-dialog').each(function() {
+				if (this != self.uiDialog[0]) {
+					maxZ = Math.max(maxZ, $(this).css('z-index'));
+				}
+			});
+			$.ui.dialog.maxZ = maxZ;
+		}
 	},
 
 	isOpen: function() {
@@ -572,6 +583,13 @@ $.extend($.ui.dialog.overlay, {
 		}
 
 		$el.remove();
+
+		// adjust the maxZ to allow other modal dialogs to continue to work (see #4309)
+		var maxZ = 0;
+		$.each(this.instances, function() {
+			maxZ = Math.max(maxZ, this.css('z-index'));
+		});
+		this.maxZ = maxZ;
 	},
 
 	height: function() {