resize2fs: don't fail when shrinking an empty file system

This commit fixes a failure when running the commands:

dd if=/dev/zero of=fs bs=1k count=100k; mke2fs fs; resize2fs -Mp fs

We should not try truncating the file system if there is only a single
block group in the file system.

Addresses-Sourceforge-Bug: #3404051

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
1 file changed