SITL: fix may-be-used-uninitialised error in thermalling code

libraries/SITL/SIM_Aircraft.cpp

@@ -35,6 +35,7 @@
 #include <AP_Declination/AP_Declination.h>
 #include <AP_Terrain/AP_Terrain.h>
 #include <AP_Scheduler/AP_Scheduler.h>
+#include <AP_BoardConfig/AP_BoardConfig.h>
 
 using namespace SITL;
 
@@ -1033,6 +1034,8 @@ float Aircraft::get_local_updraft(const Vector3d &currentPos)
     int n_thermals = 0;
 
     switch (scenario) {
+        case 0:
+            return 0;
         case 1:
             n_thermals = 1;
             thermals_w[0] =  2.0;
@@ -1054,6 +1057,8 @@ float Aircraft::get_local_updraft(const Vector3d &currentPos)
             thermals_x[0] = -180.0;
             thermals_y[0] = -260.0;
             break;
+        default:
+            AP_BoardConfig::config_error("Bad thermal scenario");
     }
 
     // Wind drift at this altitude