Fix return setting last exit code (#14120)

# Description

Fixes #14113 and #14112.

# Tests + Formatting

Added a test.

crates/nu-cli/src/util.rs

@@ -221,7 +221,7 @@ pub fn eval_source(
             report_shell_error(engine_state, &err);
             let code = err.exit_code();
             stack.set_last_error(&err);
-            code
+            code.unwrap_or(0)
         }
     };