Error pushing new branch: value too great for base (error token is...

I had written the following code to check whether a push is for branch deletion:

#!/bin/bash

NULL="0000000000000000000000000000000000000000"

while read old_sha new_sha refname ; do
    echo "Stdin: [$old_sha] [$new_sha] [$refname]"

    if [[ "$new_sha" -eq "$NULL" ]]; then   # Line 17
        echo "Skipping checks..."
        continue
    fi
    ...
    ...
    ...
done

While it works fine for branch deletion, i noticed that if i create a branch and push it to remote, i get the following error due to the above-mentioned code:

$ git push origin rel-a Counting objects: 5, done. Delta compression using up to 4 threads. Compressing objects: 100% (2/2), done. Writing objects: 100% (3/3), 407 bytes | 0 bytes/s, done. Total 3 (delta 0), reused 0 (delta 0) remote: Stdin: [0000000000000000000000000000000000000000] [9226289d2416af4cb7365d7aaa5e382bdb3d9a89] [refs/heads/rel-a] remote: remote: hooks/pre-receive: line 17: [[: 9226289d2416af4cb7365d7aaa5e382bdb3d9a89: value too great for base (error token is "922628 9d2416af4cb7365d7aaa5e382bdb3d9a89")

Although the new branch gets pushed to remote but i'm not sure why i'm getting this error and how can i fix it. I checked online and i get few links where folks had similar issue but in each such case, the error token was 08 or 09. I still tried the suggestion of using "10#" in front of my $new_sha variable but to no avail.

Any suggestions?