Yes, but then there's this oddity..
If you set $con::warnUndefinedVariables to true and then type echo($test);, it will display $test as being undefined. However, if you type echo($test = "");, there will be no "undefined" warning. Even if you set the variable to "", the variable still exists and takes up memory until you call deleteVariables("$test");, so it's not exactly null.
Null in programming languages is 0x00. The keyword null that you're used to in other programming languages literally sets the value of a variable to 0x00, regardless of type. Torque doesn't have a null keyword, but it uses C Strings for its string values which are terminated by a null char (0x00) so a string with no value ("") is simply represented as 0x00.
There's a difference between undefined variables and variables that have null as their value. If you set $someVariable equal to "", it will be defined yet have a null value. However, Torque doesn't make you declare all variables before you can use and reference them. To get around the inevitable memory access error when you try to access a memory address that doesn't exist, it does a quick check for the variable and returns null if it doesn't exist. Because of this, we can use "" to check if a variable is undefined. However, this is irrelevant to the initial point. The initial point is that "" is a null value, which is generally referred to in computing as lacking a value.
