Remove unnecessary null check in FastScroller

        final View track = mTrackImage;

        final View thumb = mThumbImage;

        final Rect container = mContainerRect;

        final int containerWidth = container.width();

        final int widthMeasureSpec = MeasureSpec.makeMeasureSpec(containerWidth, MeasureSpec.AT_MOST);

        final int maxWidth = container.width();

        final int widthMeasureSpec = MeasureSpec.makeMeasureSpec(maxWidth, MeasureSpec.AT_MOST);

        final int heightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);

        track.measure(widthMeasureSpec, heightMeasureSpec);

        final int trackWidth = track.getMeasuredWidth();

        final int thumbHalfHeight = thumb == null ? 0 : thumb.getHeight() / 2;

        final int thumbHalfHeight = thumb.getHeight() / 2;

        final int left = thumb.getLeft() + (thumb.getWidth() - trackWidth) / 2;

        final int right = left + trackWidth;

        final int top = container.top + thumbHalfHeight;