ptx: fix panic when reference length exceeds line width (#9816)

Co-authored-by: Sylvestre Ledru <sylvestre@debian.org>

Author: CrazyRoka

src/uu/ptx/src/ptx.rs

@@ -788,7 +788,9 @@ fn write_traditional_output(
         } else {
             0
         };
-        config.line_width -= max_ref_len;
+
+        // Use saturating_sub to prevent panic if the reference is wider than the line width.
+        config.line_width = config.line_width.saturating_sub(max_ref_len);
     }
 
     for word_ref in words {

tests/by-util/test_ptx.rs

@@ -338,3 +338,12 @@ fn test_unicode_truncation_alignment() {
         .succeeds()
         .stdout_only("     /   bar\n        föö/\n");
 }
+
+#[test]
+fn test_narrow_width_with_long_reference_no_panic() {
+    new_ucmd!()
+        .args(&["-w", "1", "-A"])
+        .pipe_in("content")
+        .succeeds()
+        .stdout_only(":1       content\n");
+}