Bugfix: make it work on FG next

The problem was that `next` changes the way strings are coerced to
booleans when calling `getBoolValue()` on properties.

On FG 2020.3, the string "0" is first converted to integer, which gives
0, and then to boolean, which keeps it as 0 (false).

On FG Next, "0" is interpreted as a non-empty string, and directly
converted to boolean as 1 (true).

addon-main.nas

@@ -100,7 +100,7 @@ var toFlightplan = func (ofp, fp=nil) {
     var sidID = nil;
     var starID = nil;
     foreach (var ofpFix; ofpFixes) {
-        if (ofpFix.getNode('is_sid_star').getBoolValue()) {
+        if (ofpFix.getNode('is_sid_star').getValue() == 1) {
             if ((ofpFix.getValue('stage') == 'CLB') and
                 (getprop('/sim/simbrief/options/import-departure') or 0) and
                 (sidID == nil)) {
@@ -159,6 +159,7 @@ var toFlightplan = func (ofp, fp=nil) {
     # we have everything we need; it's now safe-ish to overwrite or
     # create the actual flightplan
 
+
     if (fp == nil) {
         fp = createFlightplan();
     }