Latest release broke my implementation for COG

With small geotiffs (<1000x1000), the latest release causes an error

`Error: No image at index 4`

With large geotiffs (5000x5000+) this is not a problem. I have fixed it by relying on version 1.0.0. The no image at index issue is altered by the pyramiding for the COG.

In GDAL, pyramiding a TIF with:

`!gdaladdo -r average -ro ../data.tif 2 4 8 16`

will cause a `No image at index 4` error, while pyramiding with:

`!gdaladdo -r average -ro ../data.tif 2 4 8 16 32`

will cause a `No image at index 5` error

I am using `georaster-layer-for-leaflet` to display COGs on a leaflet webmap. My COG is loaded like so:

```javascript
var url_to_geotiff_file = "https://bucket.storage.googleapis.com/" + variable + ".tif";

parseGeoraster(url_to_geotiff_file).then(georaster => {
var layer = new GeoRasterLayer({
attribution: "",
georaster: georaster,
resolution: 768,
pixelValuesToColorFn: values => values[0] >= 0.33 ? "#6cbe76" : null,
});
```

Start by reproducing the failure with the GDAL pyramiding commands and a small COG, then trace how the JavaScript implementation handles pyramid levels and image indexes. Done means small COGs created with the reported overviews load without a “No image at index” error while larger COGs continue to work.

Written by the indexing model from the issue text.