ps.map: initialize variable contents before using them in get_ll_bounds

In some situations, when some conditionals fails, we would be assigning
uninitialized variables to values, which is undefined behavior. Fix that
by assigning a value to the variables.

This was found using cppcheck tool.

Signed-off-by: Mohan Yelugoti <ymdatta.work@gmail.com>

ps/ps.map/do_geogrid.c

@@ -300,6 +300,7 @@ void get_ll_bounds(double *w, double *e, double *s, double *n)
     double ew, ns;
     int first;
 
+    east = west = north = south = 0.0;
     e1 = PS.w.east;
     w1 = PS.w.west;
     n1 = PS.w.north;