I used app icon generator to generate icons to iphone and iPad. It give content json file below. I've add this file and then filled the icons from xcode. It help me to avoid this error. https://www.appicon.co/ this site help me with generating icons

{
  "images": [
    {
      "size": "60x60",
      "expected-size": "180",
      "filename": "180.png",
      "folder": "Assets.xcassets/AppIcon.appiconset/",
      "idiom": "iphone",
      "scale": "3x"
    },
    {
      "size": "40x40",
      "expected-size": "80",
      "filename": "80.png",
      "folder": "Assets.xcassets/AppIcon.appiconset/",
      "idiom": "iphone",
      "scale": "2x"
    },
    {
      "size": "40x40",
      "expected-size": "120",
      "filename": "120.png",
      "folder": "Assets.xcassets/AppIcon.appiconset/",
      "idiom": "iphone",
      "scale": "3x"
    },
    {
      "size": "60x60",
      "expected-size": "120",
      "filename": "120.png",
      "folder": "Assets.xcassets/AppIcon.appiconset/",
      "idiom": "iphone",
      "scale": "2x"
    },
    {
      "size": "57x57",
      "expected-size": "57",
      "filename": "57.png",
      "folder": "Assets.xcassets/AppIcon.appiconset/",
      "idiom": "iphone",
      "scale": "1x"
    },
    {
      "size": "29x29",
      "expected-size": "58",
      "filename": "58.png",
      "folder": "Assets.xcassets/AppIcon.appiconset/",
      "idiom": "iphone",
      "scale": "2x"
    },
    {
      "size": "29x29",
      "expected-size": "29",
      "filename": "29.png",
      "folder": "Assets.xcassets/AppIcon.appiconset/",
      "idiom": "iphone",
      "scale": "1x"
    },
    {
      "size": "29x29",
      "expected-size": "87",
      "filename": "87.png",
      "folder": "Assets.xcassets/AppIcon.appiconset/",
      "idiom": "iphone",
      "scale": "3x"
    },
    {
      "size": "57x57",
      "expected-size": "114",
      "filename": "114.png",
      "folder": "Assets.xcassets/AppIcon.appiconset/",
      "idiom": "iphone",
      "scale": "2x"
    },
    {
      "size": "20x20",
      "expected-size": "40",
      "filename": "40.png",
      "folder": "Assets.xcassets/AppIcon.appiconset/",
      "idiom": "iphone",
      "scale": "2x"
    },
    {
      "size": "20x20",
      "expected-size": "60",
      "filename": "60.png",
      "folder": "Assets.xcassets/AppIcon.appiconset/",
      "idiom": "iphone",
      "scale": "3x"
    },
    {
      "size": "1024x1024",
      "filename": "1024.png",
      "expected-size": "1024",
      "idiom": "ios-marketing",
      "folder": "Assets.xcassets/AppIcon.appiconset/",
      "scale": "1x"
    },
    {
      "size": "40x40",
      "expected-size": "80",
      "filename": "80.png",
      "folder": "Assets.xcassets/AppIcon.appiconset/",
      "idiom": "ipad",
      "scale": "2x"
    },
    {
      "size": "72x72",
      "expected-size": "72",
      "filename": "72.png",
      "folder": "Assets.xcassets/AppIcon.appiconset/",
      "idiom": "ipad",
      "scale": "1x"
    },
    {
      "size": "76x76",
      "expected-size": "152",
      "filename": "152.png",
      "folder": "Assets.xcassets/AppIcon.appiconset/",
      "idiom": "ipad",
      "scale": "2x"
    },
    {
      "size": "50x50",
      "expected-size": "100",
      "filename": "100.png",
      "folder": "Assets.xcassets/AppIcon.appiconset/",
      "idiom": "ipad",
      "scale": "2x"
    },
    {
      "size": "29x29",
      "expected-size": "58",
      "filename": "58.png",
      "folder": "Assets.xcassets/AppIcon.appiconset/",
      "idiom": "ipad",
      "scale": "2x"
    },
    {
      "size": "76x76",
      "expected-size": "76",
      "filename": "76.png",
      "folder": "Assets.xcassets/AppIcon.appiconset/",
      "idiom": "ipad",
      "scale": "1x"
    },
    {
      "size": "29x29",
      "expected-size": "29",
      "filename": "29.png",
      "folder": "Assets.xcassets/AppIcon.appiconset/",
      "idiom": "ipad",
      "scale": "1x"
    },
    {
      "size": "50x50",
      "expected-size": "50",
      "filename": "50.png",
      "folder": "Assets.xcassets/AppIcon.appiconset/",
      "idiom": "ipad",
      "scale": "1x"
    },
    {
      "size": "72x72",
      "expected-size": "144",
      "filename": "144.png",
      "folder": "Assets.xcassets/AppIcon.appiconset/",
      "idiom": "ipad",
      "scale": "2x"
    },
    {
      "size": "40x40",
      "expected-size": "40",
      "filename": "40.png",
      "folder": "Assets.xcassets/AppIcon.appiconset/",
      "idiom": "ipad",
      "scale": "1x"
    },
    {
      "size": "83.5x83.5",
      "expected-size": "167",
      "filename": "167.png",
      "folder": "Assets.xcassets/AppIcon.appiconset/",
      "idiom": "ipad",
      "scale": "2x"
    },
    {
      "size": "20x20",
      "expected-size": "20",
      "filename": "20.png",
      "folder": "Assets.xcassets/AppIcon.appiconset/",
      "idiom": "ipad",
      "scale": "1x"
    },
    {
      "size": "20x20",
      "expected-size": "40",
      "filename": "40.png",
      "folder": "Assets.xcassets/AppIcon.appiconset/",
      "idiom": "ipad",
      "scale": "2x"
    }
  ]
}