Fix get -i ignoring errors for only the first cellpath (#11213)

# Description
Fixes issue #11212 where only the first cellpath supplied to `get -i` is
treated as optional, and the rest of the cell paths are treated as
non-optional.

# Tests
Added one test.

crates/nu-command/tests/commands/get.rs

@@ -200,3 +200,10 @@ fn ignore_errors_works() {
 
     assert_eq!(actual.out, "null");
 }
+
+#[test]
+fn ignore_multiple() {
+    let actual = nu!(r#"[[a];[b]] | get -i c d | to nuon"#);
+
+    assert_eq!(actual.out, "[[null], [null]]");
+}