CB is a logic input with no internal pullup or pulldown, therefore if CB is left floating the voltage is indeterminate; it can be either high or low. If the switch outputs are enabled (/EN\\ is driven low) and CB is floating, there is no guarantee of the switch states--COM_ could be connected to either NO_ or NC_. If the switch outputs are disabled (/EN\\ is driven high), then the switch states are guaranteed to be high impedance, COM_ is connected to neither NO_ nor NC_.
It is always best practice to not leave logic inputs floating, but rather pull them high or low to the supply rail. Leaving a logic input floating can cause the supply current to increase around the threshold region. The MAX4948 datasheet provides a typical VCC supply current vs. logic input voltage plot as shown below: