Is electricity wasted when you've turned on a switch, but are not using it?

Before we get to the answer let us first understand the basics of electrical plugs and sockets.
An electrical plug and a socket will have 3 pins- Earth, Live, Neutral.

Earth wire- It is a safety wire and connects the metal case of the appliance to the earth (we will not be talking about this here)

Live wire- The live wire carries current to the appliance.

Neutral wire- The neutral wire completes the circuit and carries current away from the appliance

That means, for a device to work the electric current from the socket must enter the live wire/pin in the plug, power the appliance connected and return through the neutral wire/pin completing the circuit. All this while the switch is on.

This is shown in the circuit diagram below.

Ls, Ns- Live wire, Neutral wire of socket.

Lp, Np- Live wire, Neutral wire of plug.

The switch is "ON" and the plug is inserted into the socket (Ls-Lp and Ns-Np are shorted). The current takes the path as shown(Blue colour lines), the device/appliance is powered and electricity is consumed. 

Now if the switch is ON and we have not connected any device to the socket i.e we are not using it.

We can see that there is no connection between Ls-Lp and Ns-Np. It is an open circuit even when the switch is ON. There is no current/electricity in the circuit. Therefore electricity is not wasted.

There are mobile chargers with an led that light up by just switching on, even without the mobile being connected.

You can see that the transformer is powered and there is voltage drop at the secondary of the transformer. This is being utilized by the led. The second branch is an open circuit as the mobile is not connected.