Sorry about this issue. Looking through the iOS build logs, I see:
Error: Unable to render destination image
<CGColor 0x7ff2b1506d70> [<CGColorSpace 0x7ff2b1507e80> (kCGColorSpaceDeviceRGB)] ( 0 0 0 1 )
I am not sure what exactly could be causing this, but it looks like there is an issue with one or more of the images you are using in your app icon or loading screen. I recommend making sure they are the correct file extension (e.g. save PNG files as .png) and you may want to try re-encoding these files with a popular image encoder like ImageMagick or optipng.