Take care to not dereference the original image a second time

vips.go

@@ -318,7 +318,12 @@ func vipsSave(image *C.VipsImage, o vipsSaveOptions) ([]byte, error) {
 	if err != nil {
 		return nil, err
 	}
+	//When an image has an unsupported color space, vipsPreSave returns the pointer of the image passed to it unmodified.
+	//When this occurs, we must take care to not dereference the original image a second time;
+	//we may otherwise erroneously free the object twice
+	if tmpImage != image {
 		defer C.g_object_unref(C.gpointer(tmpImage))
+	}
 
 	length := C.size_t(0)
 	saveErr := C.int(0)