User has to enter at least one character to be able to save the sensor's new name

[isabelrios]

Build tested: 198ed59

Steps Tap on a sensor to favorite it Tap directly on Save button

Expected The Save/Done button is disabled till user enter at least one char, then the button is active and the new name of the sensor is shown.

Actual The Save/Done button is always active. User can tap on it without entering any letter. The sensor will be named as 'Sensor'