I will bet that the air that is in the fuel filter is under pressure, which means that as soon as the float needle comes off the seat, the fuel pump and the residual pressure of that air will force fuel to go to the carburetor. This "trapped" air can't get out since it above the down pipe/filter element of the filter. Now if you have a leaky gasket where the glass bowl meets the filter housing, there will not be air in the filter, but there will be a fuel leak.
In other words, don't worry, be happy.
Carl
