Format: format empty arrays as nothing

defmt/src/export/mod.rs

@@ -185,7 +185,13 @@ pub fn u8_array(a: &[u8]) {
 
 // NOTE: This is passed `&[u8; N]` – it's just coerced to a slice.
 pub fn fmt_array<T: Format>(a: &[T]) {
-    fmt_slice(a)
+    if let Some((first, remainder)) = a.split_first() {
+        istr(&first._format_tag());
+        first._format_data();
+        for value in remainder {
+            value._format_data();
+        }
+    }
 }
 
 /// Implementation detail

defmt/tests/encode.rs

@@ -557,6 +557,15 @@ fn slice() {
             23u8,             // val[0]
             42u8,             // val[1]
         ],
+    );
+
+    let val: &[u8] = &[];
+    check_format!(
+        val,
+        [
+            inc(index, 2),    // "{=[?]}"
+            val.len() as u32, // length
+        ],
     )
 }
 
@@ -737,7 +746,6 @@ fn format_arrays() {
         &array,
         [
             index,         // "{=[?;0]}"
-            inc(index, 1), // "{=u16}"
         ]
     );