Stop the initialization of a ZIP or Magneto-Optical drive if its task file structure pointer is NULL.

src/disk/mo.c

@@ -2152,6 +2152,9 @@ mo_hard_reset(void)
 
             mo_init(dev);
 
+            if (dev->tf == NULL)
+                continue;
+
             if (strlen(mo_drives[c].image_path))
                 mo_load(dev, mo_drives[c].image_path);
 

src/disk/zip.c

@@ -2391,6 +2391,9 @@ zip_hard_reset(void)
 
             zip_init(dev);
 
+            if (dev->tf == NULL)
+                continue;
+
             if (strlen(zip_drives[c].image_path))
                 zip_load(dev, zip_drives[c].image_path);