How to avoid throwing an exceptions for a built-in function?

[k-five via Digitalmars-d-learn]

I have a line of code that uses "to" function in std.conv for a 
purpose like:

int index = to!int( user_apply[ 4 ] ); // string to int

When the user_apply[ 4 ] has value, there is no problem; but when 
it is empty: ""
it throws an ConvException exception and I want to avoid this 
exception.

currently I have to use a dummy catch:
try{
     index = to!int( user_apply[ 4 ] );
} catch( ConvException conv_error ){
     // nothing
}

I no need to handle that, so is there any way to prevent this 
exception?