Fix opening/closing gifv sometimes making the timeline scroll

app/javascript/flavours/glitch/components/media_gallery.js

@@ -82,11 +82,6 @@ class Item extends React.PureComponent {
     e.stopPropagation();
   }
 
-  handleMouseDown = (e) => {
-    e.preventDefault();
-    e.stopPropagation();
-  }
-
   render () {
     const { attachment, index, size, standalone, letterbox, displayWidth } = this.props;
 
@@ -190,7 +185,6 @@ class Item extends React.PureComponent {
             onClick={this.handleClick}
             onMouseEnter={this.handleMouseEnter}
             onMouseLeave={this.handleMouseLeave}
-            onMouseDown={this.handleMouseDown}
             autoPlay={autoPlay}
             loop
             muted

app/javascript/flavours/glitch/components/modal_root.js

@@ -40,7 +40,7 @@ export default class ModalRoot extends React.PureComponent {
       this.setState({ revealed: false });
     }
     if (!nextProps.children && !!this.props.children) {
-      this.activeElement.focus();
+      this.activeElement.focus({ preventScroll: true });
       this.activeElement = null;
     }
   }

app/javascript/flavours/glitch/styles/components/media.scss

@@ -147,6 +147,7 @@
   position: relative;
   z-index: 1;
   object-fit: contain;
+  user-select: none;
 
   &:not(.letterbox) {
     height: 100%;