Show error messages in UI if something goes wrong

cmd/backend/images.go

@@ -2,6 +2,7 @@ package backend
 
 import (
 	"fmt"
+	"image"
 	"io"
 	"os"
 
@@ -10,9 +11,14 @@ import (
 	"github.com/google/uuid"
 )
 
+var ErrUnsupportedFormat error = image.ErrFormat // used internally by imaging
+
 func SaveImage(c *Config, src io.Reader) (string, error) {
 	img, err := imaging.Decode(src, imaging.AutoOrientation(true))
 	if err != nil {
+		if err == ErrUnsupportedFormat {
+			return "", ErrUnsupportedFormat
+		}
 		return "", fmt.Errorf("error decoding image: %v", err)
 	}