Index: wp-includes/media.php
===================================================================
--- wp-includes/media.php	(revision 22967)
+++ wp-includes/media.php	(working copy)
@@ -1660,7 +1660,7 @@
 			<div class="details">
 				<div class="filename">{{ data.filename }}</div>
 				<div class="uploaded">{{ data.dateFormatted }}</div>
-				<# if ( 'image' === data.type && ! data.uploading ) { #>
+				<# if ( 'image' === data.type && ! data.uploading && data.width && data.height ) { #>
 					<div class="dimensions">{{ data.width }} &times; {{ data.height }}</div>
 				<# } #>
 				<# if ( ! data.uploading ) { #>