navradio: fix crash spotted by Torsten, when nav range is unspecified.

diff --git a/src/Instrumentation/navradio.cxx b/src/Instrumentation/navradio.cxx
index cf05bc76495ffcdc63d158221e59f32611b1ad2b..19e29a226f0cf0e121f71614876e7ee7db13accf 100644 (file)
--- a/src/Instrumentation/navradio.cxx
+++ b/src/Instrumentation/navradio.cxx
@@ -271,6 +271,10 @@ FGNavRadio::unbind ()
 double FGNavRadio::adjustNavRange( double stationElev, double aircraftElev,
                                  double nominalRange )
 {
+    if (nominalRange < 0.0) {
+      nominalRange = FG_NAV_DEFAULT_RANGE;
+    }
+    
     // extend out actual usable range to be 1.3x the published safe range
     const double usability_factor = 1.3;
 
@@ -454,7 +458,7 @@ void FGNavRadio::updateReceiver(double dt)
            effective_range
                 = adjustNavRange( nav_elev, pos.getElevationM(), _navaid->get_range() );
        }
-
+  
   double effective_range_m = effective_range * SG_NM_TO_METER;
 
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