Typevisitor not collecting constraints correctly

There is an issue with the type visitor and how it is handling visiting statements. This causes a NoneType to try to be concatenated to a string. The issue arises when parsing the following snippet:

module mod
stationary stat
manifest aaa
manifest bbb
manifest ccc
manifest ddd

functions:

instructions:

x = 0
if ( 3 == 3) {
    x = 3
} else {
    x = 5
}
y = x

Using the following execution flags:
-d -i resources/programs/scratch_pad.bs -p ./resources/ -t inkwell

Reproduce el fallo con el fragmento de BioScript proporcionado y los flags -d -i resources/programs/scratch_pad.bs -p ./resources/ -t inkwell. Inspecciona el manejo de sentencias del visitante de tipos y la recopilación de restricciones; se considera terminado cuando el ejemplo se analiza sin un error de concatenación de cadenas de NoneType y recopila sus restricciones correctamente.