JS: Fix Allowing ++ and -- input changes to reflect in input tokens for keyed inputs
JS: Fix Allowing ++ and -- input changes to reflect in input tokens for keyed inputs

Consider the case when valueTokens is null

Signed-off-by: Stephen Wong <6f34db11dd2258ec4ffa799eb0d7827f906cb1c6@ausenco.com>

jaamsim/jaamsim,jaamsim/jaamsim,jaamsim/jaamsim,jaamsim/jaamsim