Fixed segmentation fault if no ADRV9002 device is found

[free43]

PR Description

• Segmentation fault is happening, when trying to load the plugin ADRV9002, if none of this devices are found in the current context. Therefore I checked if the plugin_info is NULL to prevent a segmentation fault.
• If no adrv9002 are found, the plugin will not be loaded.

PR Type

• Bug fix (a change that fixes an issue)
• New feature (a change that adds new functionality)
• Breaking change (a change that affects other repos or cause CIs to fail)

PR Checklist

• I have followed the coding standards and guidelines
• I have conducted a self-review of my own code changes
• I have commented new code, particulary complex or unclear areas
• I have checked in CI output that no new warnings/errors got introduced
• I have updated documentation accordingly (GitHub Pages, READMEs, etc)

[dNechita]

Looks good. Thank you for contributing!