Removing unused code
The LabVIEW compiler removes any unused code, code that is inside a case that will never execute is excluded form the compiled code. This gives the infamous warning on 8+ systems that opens a 7- VI where a case structure that is fed by a constant, the constant is replaced by a hidden control to maintain compatibility.
The upper part tries to get a caption for a control that doesn't have a caption. Normally this would through an error, but the compiler doesn't execute the property because the caption reference isn't wired. The lower part uses the caption reference and troughs an error.