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

Author: Your Name

src/decoder/image.rs

@@ -145,12 +145,15 @@ impl Image {
                     .map(SampleFormat::from_u16_exhaustive)
                     .collect();
 
+                let Some(format) = sample_format.first().copied() else {
+                    // Reject empty sample formats
+                    return Err(TiffFormatError::InvalidTagValueType(Tag::SampleFormat).into());
+                };
                 // TODO: for now, only homogenous formats across samples are supported.
-                if !sample_format.windows(2).all(|s| s[0] == s[1]) {
+                if !sample_format.iter().all(|&s| s == format) {
                     return Err(TiffUnsupportedError::UnsupportedSampleFormat(sample_format).into());
                 }
-
-                sample_format[0]
+                format
             }
             None => SampleFormat::Uint,
         };

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 {