Installation script fails: version resolves to "null" instead of latest release

[alon-blyachman]

The gnmic installation script fails to properly detect the latest version, resulting in "null" being used in the download URL path.

Steps to Reproduce
Run the official installation command: curl -sL https://get-gnmic.openconfig.net | bash
Expected Behavior
The script should:

Detect the latest gnmic release version
Download the correct tarball (e.g., gnmic_0.x.x_linux_x86_64.tar.gz)
Successfully extract and install gnmic
Actual Behavior
The script attempts to download from an invalid URL:

Downloading https://github.com/openconfig/gnmic/releases/download/null/gnmic_ull_linux_x86_64.tar.gz
tar: This does not look like a tar archive
The version is resolved to null instead of the actual latest version number, causing the download to fail.

Environment
OS: Linux x86_64
Installation method: Official install script from get-gnmic.openconfig.net