top: fix unlikely edge case wherein all fields are off

While testing a newlib interface for pids acquisitions
I encountered some unexpected results if an idiot user
(me) turns off all displayable fields. So, this commit
ensures that the PID field will be shown as a minimum.

Signed-off-by: Jim Warner <james.warner@comcast.net>

top/top.c

@@ -1994,6 +1994,7 @@ static void calibrate_fields (void) {
 #endif
             }
          }
+         if (!w->totpflgs) w->pflgsall[w->totpflgs++] = EU_PID;
 
          /* build a preliminary columns header not to exceed screen width
             while accounting for a possible leading window number */