src/signature: Initialize autoptr variable 'file' in cms_verify_file()
src/signature: Initialize autoptr variable 'file' in cms_verify_file()

This needs to initialized to NULL to allow proper handling of autopr
functionality.

Signed-off-by: Enrico Jorns <a2e5f936c390f36494e46e71bcfbe365bb1e8c49@pengutronix.de>

jluebbe/rauc,ejoerns/rauc,ejoerns/rauc,rauc/rauc,jluebbe/rauc,jluebbe/rauc,rauc/rauc,ejoerns/rauc,rauc/rauc