express: Fix VirtualFileMountZip not having init_type() called

panda/src/express/config_express.cxx

@@ -26,6 +26,7 @@
 #include "virtualFileMountMultifile.h"
 #include "virtualFileMountRamdisk.h"
 #include "virtualFileMountSystem.h"
+#include "virtualFileMountZip.h"
 #include "virtualFileSimple.h"
 #include "fileReference.h"
 #include "temporaryFile.h"
@@ -116,6 +117,7 @@ init_libexpress() {
   VirtualFileMountMultifile::init_type();
   VirtualFileMountRamdisk::init_type();
   VirtualFileMountSystem::init_type();
+  VirtualFileMountZip::init_type();
   VirtualFileSimple::init_type();
   FileReference::init_type();
   TemporaryFile::init_type();