Wrapped modal.less into a mixin which gets rid of the last file which emitted CSS

customize.dist/src/less2/include/fileupload.less

@@ -1,8 +1,9 @@
 @import (reference) './colortheme-all.less';
-@import (once) './modal.less';
+@import (reference) './modal.less';
 
 .fileupload_main () {
     /* Upload status table */
+    modal_main();
     #cp-fileupload {
         .modal_base();
         position: absolute;