[lib][fs][9p] fail mount gracefully if bdev isn't passed
diff --git a/lib/fs/9p/v9fs.c b/lib/fs/9p/v9fs.c
index eaedee2..c4555fe 100644
--- a/lib/fs/9p/v9fs.c
+++ b/lib/fs/9p/v9fs.c
@@ -91,6 +91,10 @@
 
     LTRACEF("bdev (%p) cookie (%p)\n", dev, cookie);
 
+    if (!dev) {
+        return ERR_INVALID_ARGS;
+    }
+
     v9fs_t *v9fs = calloc(1, sizeof(v9fs_t));
 
     if (!v9fs)