Empty TIFF files while exporting images using Google Earth Engine

I am trying to export aerial images of a city in Japan. I have specified a polygon geometry of the location and also specified it as region in export. But I am getting blank TIFFs in the drive as output. What could have gone wrong?

print('started running script');
var landsat8_col = {
  l8_reflect_tier1:ee.ImageCollection("LANDSAT/LC08/C01/T1_SR"),
  l8_reflect_tier2:ee.ImageCollection("LANDSAT/LC08/C01/T2_SR"),
  l8_atmosphere_tier1:ee.ImageCollection("LANDSAT/LC08/C01/T1_TOA"),
  l8_atmosphere_tier2:ee.ImageCollection("LANDSAT/LC08/C01/T2_TOA"),
  l8_raw_tier1:ee.ImageCollection("LANDSAT/LC08/C01/T1"),
  l8_raw_tier2:ee.ImageCollection("LANDSAT/LC08/C01/T2")
}

var landsat7_col = {
  l7_reflect_tier1:ee.ImageCollection("LANDSAT/LC07/C01/T1_SR"),
  l7_reflect_tier2:ee.ImageCollection("LANDSAT/LC07/C01/T2_SR"),
  l7_atmosphere_tier1:ee.ImageCollection("LANDSAT/LC07/C01/T1_TOA"),
  l7_atmosphere_tier2:ee.ImageCollection("LANDSAT/LC07/C01/T2_TOA"),
  l7_raw_tier1:ee.ImageCollection("LANDSAT/LC07/C01/T1"),
  l7_raw_tier2:ee.ImageCollection("LANDSAT/LC07/C01/T2")
}

var l8_dates = [['2015-01-01','2018-05-31']]

var l7_dates = [['2008-01-01','2008-12-31']]

var point_of_interest = ee.Geometry.Point([137.95,35.72])

var polygon_of_interest = ee.Geometry.Polygon([
          [
            [
              137.93982982635498,
              35.728313419207375
            ],
            [
              137.94046819210052,
              35.728313419207375
            ],
            [
              137.94046819210052,
              35.729663398270645
            ],
            [
              137.93982982635498,
              35.729663398270645
            ],
            [
              137.93982982635498,
              35.728313419207375
            ]
          ]
        ]);

var l8_keys = Object.keys(landsat8_col)
var l7_keys = Object.keys(landsat7_col)


var l8_values = Object.keys(landsat8_col).map(function(key) {
    return landsat8_col[key];
});
var l7_values = Object.keys(landsat7_col).map(function(key) {
    return landsat7_col[key];
});

function getFilteredImages(img_collections,dates,point_of_interest){
  var filtered_imgs = [];
  img_collections.forEach(function(img_collection){
    var img = img_collection.filterBounds(geometry).filterDate(dates[0][0],dates[0][1]).sort('CLOUD_COVER').first();
    filtered_imgs.push(img);
    print(img);
  });
  return filtered_imgs;
}


function export_images(imgs_col){
  for(var i=0;i<imgs_col.length;i++){
    Export.image.toDrive({
      image: imgs_col[i].select(['B4','B3','B2']),
      description: l8_keys[i],
      scale: 1000,
      maxPixels:1e13,
      region:polygon_of_interest,
      fileFormat: 'GeoTIFF',
      folder:"2"
    });
  }
}


var filtered_imgs = getFilteredImages(l8_values,l8_dates,point_of_interest);
var vizParams = {
  bands: ['B4', 'B3', 'B2'],
  min: 0,
  max:1000,
  gamma: [0.95, 1.5, 2]
};

export_images(filtered_imgs);
print('Done');