fix panic if empty

src/utils/ext.rs

@@ -48,6 +48,10 @@ impl SliceExt for [u8] {
                 },
             );
 
+        if self[start..].is_empty() {
+            return &[]
+        }
+
         &self[start..=end]
     }
 

tests/data/markdown.md

@@ -0,0 +1,14 @@
+# 14 lines 4 code 7 comments 3 blanks
+Sit dicta esse doloremque officia iusto? Assumenda alias aperiam id quis
+pariatur? Libero modi harum iusto modi magni? Sit temporibus fugit facere
+nostrum culpa ipsum totam! Reprehenderit praesentium obcaecati nemo.
+
+```rust
+use std::println;
+
+fn main () {
+    // Comment
+    println!("Hello World!");
+}
+```
+