tape: add TapeDensity::Unknown

src/api2/types/tape/drive.rs

@@ -119,6 +119,8 @@ pub struct MamAttribute {
 #[api()]
 #[derive(Serialize,Deserialize,Copy,Clone,Debug)]
 pub enum TapeDensity {
+    /// Unknown (no media loaded)
+    Unknown,
     /// LTO1
     LTO1,
     /// LTO2
@@ -144,6 +146,7 @@ impl TryFrom<u8> for TapeDensity {
 
     fn try_from(value: u8) -> Result<Self, Self::Error> {
         let density = match value {
+            0x00 => TapeDensity::Unknown,
             0x40 => TapeDensity::LTO1,
             0x42 => TapeDensity::LTO2,
             0x44 => TapeDensity::LTO3,