Fix typo

src/eval.c

@@ -1346,7 +1346,7 @@ evaluate_assignment(apfl_ctx ctx, struct apfl_expr_assignment *assignment)
         ctx,
         &pattern,
         stack_must_get(ctx, -1) // stack_must_get instead of stack_must_pop,
-                                // so the value is stull on the stack on return.
+                                // so the value is still on the stack on return.
     );
 
     match_pattern_deinit(ctx, &pattern);