core: Fix crash when cutting/pasting single layer

When cutting and pasting a single layer,
drawables->data might be empty. This results in a
crash on Windows and a failure to paste on Linux.
Since this function is inside an IF statement that already
confirms it has a valid image, the base type and
precision are retrieved from there instead.

app/core/gimp-edit.c

@@ -520,8 +520,8 @@ gimp_edit_paste_get_layers (GimpImage     *image,
         }
 
       layers = gimp_edit_paste_get_tagged_layers (image, layers, NULL, floating_format,
-                                                  gimp_drawable_get_base_type (drawables->data),
-                                                  gimp_drawable_get_precision (drawables->data),
+                                                  gimp_image_get_base_type (image),
+                                                  gimp_image_get_precision (image),
                                                   *paste_type);
       layers = g_list_reverse (layers);
     }