checker: fix a compiler panic on `fntest()?(&int,&int){return test()?}`

vlib/v/checker/return.v

@@ -135,7 +135,7 @@ pub fn (mut c Checker) return_stmt(mut node ast.Return) {
 				pos)
 		}
 		if exp_type.is_ptr() && got_typ.is_ptr() {
-			mut r_expr := &node.exprs[i]
+			mut r_expr := &node.exprs[expr_idxs[i]]
 			if mut r_expr is ast.Ident {
 				if mut r_expr.obj is ast.Var {
 					mut obj := unsafe { &r_expr.obj }

vlib/v/checker/tests/return_optional_of_multiple_results.out

@@ -0,0 +1,6 @@
+vlib/v/checker/tests/return_optional_of_multiple_results.vv:2:9: error: `?` is not needed, use `return test()`
+    1 | fn test() ?(&int, &int) {
+    2 |     return test() ?
+      |            ~~~~~~
+    3 | }
+    4 |

vlib/v/checker/tests/return_optional_of_multiple_results.vv

@@ -0,0 +1,6 @@
+fn test() ?(&int, &int) {
+	return test() ?
+}
+
+fn main() {
+}