Fix decoder panic with malformed (empty) sample format tag

I've included a minimal reproducer in
tests/fuzz_images/oor_panic/sample-format-empty-vec.bin

src/encoder/mod.rs

@@ -37,8 +37,9 @@ pub type Predictor = crate::tags::Predictor;
 #[cfg(feature = "deflate")]
 pub type DeflateLevel = compression::DeflateLevel;
 
-#[derive(Clone, Copy, PartialEq)]
+#[derive(Clone, Copy, PartialEq, Default)]
 pub enum Compression {
+    #[default]
     Uncompressed,
     #[cfg(feature = "lzw")]
     Lzw,
@@ -47,12 +48,6 @@ pub enum Compression {
     Packbits,
 }
 
-impl Default for Compression {
-    fn default() -> Self {
-        Self::Uncompressed
-    }
-}
-
 impl Compression {
     fn tag(&self) -> CompressionMethod {
         match self {