Fix being able to un-rotate images

Since 0 is falsy, this made it impossible to return images to 0 degrees
of rotation.

Signed-off-by: Robin Townsend <robin@robin.town>

src/components/views/elements/ImageView.tsx

@@ -122,7 +122,7 @@ export default class ImageView extends React.Component<IProps, IState> {
         const image = this.image.current;
         const imageWrapper = this.imageWrapper.current;
 
-        const rotation = inputRotation || this.state.rotation;
+        const rotation = inputRotation ?? this.state.rotation;
 
         const imageIsNotFlipped = rotation % 180 === 0;