Assign the corresponding VpnProfileState for the null argument.
The varargs parameter has type "VpnProfileState...". It needs
to decide whether the implementation want the argument to be
treated as a single-element of type VpnProfileState or no
arguement. Otherwise, it will confuse the compiler and cause
warning.
Test: atest VpnTest
Change-Id: Ic1dee696bb50cd78849de4812fb46fd764b23c6e