Nest sticker image element for correct positioning of tooltips.

src/components/views/messages/MStickerBody.js

@@ -53,6 +53,7 @@ export default class MStickerBody extends MImageBody {
 
         return (
             <span className="mx_MImageBody" ref="body">
+                <div className="mx_MImageBody_thumbnail_container">
                     <img className="mx_MImageBody_thumbnail" src={thumbUrl} ref="image"
                         alt={content.body}
                         onLoad={this.props.onWidgetLoad}
@@ -60,6 +61,7 @@ export default class MStickerBody extends MImageBody {
                         onMouseLeave={this._onMouseLeave}
                     />
                     { tooltip }
+                </div>
             </span>
         );
     }