Btrfs-progs: print-tree: check num_stripes in print_chunk

Btrfs-progs: print-tree: check num_stripes in print_chunk

[TEST/fuzz] case: 004-simple-dump-tree

Since the wrong key(DATA_RELOC_TREE CHUNK_ITEM 0) in root tree,
error calling print_chunk(), resulting in num_stripes == 0.

ERROR:
     [TEST/fuzz]   004-simple-dump-tree
ctree.h:317: btrfs_chunk_item_size: BUG_ON `num_stripes == 0`
        triggered, value 1

failed (ignored, ret=134): /myproject/btrfs-progs/btrfs
inspect-internal dump-tree
/myproject/btrfs-progs/tests/fuzz-tests/images/
bko-155201-wrong-chunk-item-in-root-tree.raw.restored

test failed for case 004-simple-dump-tree
Makefile:288: recipe for target 'test-fuzz' failed
make: *** [test-fuzz] Error 1

So, check on num_stripes in print_chunk

Signed-off-by: Zhang Yu <zhangyu-fnst@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>