How can set variable-size signal with a nondiscrete sample time ?

Hi. I am facing some variable-size signal error. here in the (fig 1)attached file when I connect control input2 of switch2 with constant 1 it's running fine. however, when I connect the control input2 of switch 2 (fig2) with another block (which also gives 1 or 0), it show an error that :

The signal at input port 1 of 'ADC_Sign_E_ref_12/Switch2' is a variable-size signal with a nondiscrete sample time. The sample time for any variable-size signal must be discrete.

how can I resolve this error. could anyone please help? Thanks