Use 2*rowHeight as default for image height

front/src/Row.js

@@ -12,7 +12,9 @@ const PureTextRow = ({ row }) => (
 
 const PureImageRow = ({ row }) => {
   const style =
-    'heightFactor' in row ? { height: `calc(${row.heightFactor} * var(--rowHeight))` } : {};
+    'heightFactor' in row
+      ? { height: `calc(${row.heightFactor} * var(--rowHeight))` }
+      : { height: 'calc(2 * var(--rowHeight))' };
   return (
     <div className="bloc image-bloc" style={style}>
       <img src={row.image} alt="" />