Do not highlight timeline segments in thumbnail editor

In the thumbnail editor, a timeline similar to the one in the cutting
view is visible. One thing they share is highlighting individual
segments on the timeline. This makes no sense in the thumbnail
editor, as you cannot interact with the segments at all. This fixes
that.

Resolves #834

src/main/Thumbnail.tsx

@@ -101,6 +101,7 @@ const Thumbnail : React.FC<{}> = () => {
       />
       <Timeline
         timelineHeight={125}
+        styleByActiveSegment={false}
         selectIsPlaying={selectIsPlaying}
         selectCurrentlyAt={selectCurrentlyAt}
         setIsPlaying={setIsPlaying}

src/main/Timeline.tsx

@@ -35,13 +35,15 @@ import { ThemedTooltip } from './Tooltip';
  */
 const Timeline: React.FC<{
   timelineHeight?: number,
+  styleByActiveSegment?: boolean,
   selectCurrentlyAt: (state: RootState) => number,
   selectIsPlaying:(state: RootState) => boolean,
   setClickTriggered: ActionCreatorWithPayload<any, string>,
   setCurrentlyAt: ActionCreatorWithPayload<number, string>,
   setIsPlaying: ActionCreatorWithPayload<boolean, string>,
 }> = ({
   timelineHeight = 250,
+  styleByActiveSegment = true,
   selectCurrentlyAt,
   selectIsPlaying,
   setClickTriggered,
@@ -81,7 +83,7 @@ const Timeline: React.FC<{
     />
     <div css={{position: 'relative', height: timelineHeight - 20 + 'px'}} >
       <Waveforms timelineHeight={timelineHeight}/>
-      <SegmentsList timelineWidth={width} timelineHeight={timelineHeight} styleByActiveSegment={true} tabable={true}/>
+      <SegmentsList timelineWidth={width} timelineHeight={timelineHeight} styleByActiveSegment={styleByActiveSegment} tabable={true}/>
     </div>
   </div>
   );
@@ -283,8 +285,8 @@ export const Scrubber: React.FC<{
 export const SegmentsList: React.FC<{
   timelineWidth: number,
   timelineHeight: number,
-  styleByActiveSegment: boolean,
-  tabable: boolean,
+  styleByActiveSegment?: boolean,
+  tabable?: boolean,
 }> = ({
   timelineWidth,
   timelineHeight,