Add additional check that context lines aren't printed twice

Author: TysonAndre

run-tests.php

@@ -2955,6 +2955,9 @@ function generate_array_diff(array $ar1, array $ar2, bool $is_reg, array $w): ar
     $l2 = -2;
     $old_k1 = -1;
     $add_context_lines = function (int $new_k1) use (&$old_k1, &$diff, $w, $context_line_count, $format_context_line) {
+        if ($old_k1 >= $new_k1) {
+            return;
+        }
         $end = $new_k1 - 1;
         $range_end = min($end, $old_k1 + $context_line_count);
         if ($old_k1 >= 0) {