net: dsa: fix a crash if ->getssetcount() fails
This is an automated ID intended to aid in discovery of potential security vulnerabilities. The actual impact and attack plausibility have not yet been proven. This ID is fixed in Linux Kernel version v5.10.42 by commit caff86f85512b8e0d9830e8b8b0dfe13c68ce5b6, it was introduced in version v4.7 by commit badf3ada60ab8f76f9488dc8f5c0c57f70682f5a. For more details please see the references link.