Backport of modal positioning fix

src/modules/modal.js

@@ -456,17 +456,24 @@ $.fn.modal = function(parameters) {
           }
         },
 
+
         cacheSizes: function() {
-          module.cache = {
-            pageHeight    : $body.outerHeight(),
-            height        : $module.outerHeight() + settings.offset,
-            contextHeight : (settings.context == 'body')
-              ? $(window).height()
-              : $dimmable.height()
-          };
-          module.debug('Caching modal and container sizes', module.cache);
+          var
+            modalHeight = $module.outerHeight()
+          ;
+          if(modalHeight !== 0) {
+            module.cache = {
+              pageHeight    : $(document).outerHeight(),
+              height        : modalHeight + settings.offset,
+              contextHeight : (settings.context == 'body')
+                ? $(window).height()
+                : $dimmable.height()
+            };
+            module.debug('Caching modal and container sizes', module.cache);
+          }
         },
 
+
         can: {
           fit: function() {
             return (module.cache.height < module.cache.contextHeight);