#82 spicious warning

[Dietmar Warning]

Holger I got this with VS:
9>C:\msys64\home\warning\ngspice\src\frontend\inpcom.c(9806): warning C4701: potentially uninitialized local variable 'prevcard' used
9>C:\msys64\home\warning\ngspice\src\frontend\inpcom.c(9806): warning C4703: potentially uninitialized local pointer variable 'prevcard' used