Sanity check for Coverity #1366290.

(Vector should never be empty, especially for chosen zone).

lib/rmg/CZonePlacer.cpp

@@ -395,14 +395,17 @@ void CZonePlacer::moveOneZone(TZoneMap &zones, TForceVector &totalForces, TDista
 					targetZone = otherZone;
 				}
 			}
-			float3 vec = targetZone->getCenter() - ourCenter;
-			float newDistanceBetweenZones = (std::max(misplacedZone->getSize(), targetZone->getSize())) / mapSize;
-			logGlobal->traceStream() << boost::format("Trying to move zone %d %s towards %d %s. Old distance %f") %
-				misplacedZone->getId() % ourCenter() % targetZone->getId() % targetZone->getCenter()() % maxDistance;
-			logGlobal->traceStream() << boost::format("direction is %s") % vec();
-
-			misplacedZone->setCenter(targetZone->getCenter() - vec.unitVector() * newDistanceBetweenZones); //zones should now overlap by half size
-			logGlobal->traceStream() << boost::format("New distance %f") % targetZone->getCenter().dist2d(misplacedZone->getCenter());
+			if (targetZone) //TODO: consider refactoring duplicated code
+			{
+				float3 vec = targetZone->getCenter() - ourCenter;
+				float newDistanceBetweenZones = (std::max(misplacedZone->getSize(), targetZone->getSize())) / mapSize;
+				logGlobal->traceStream() << boost::format("Trying to move zone %d %s towards %d %s. Old distance %f") %
+					misplacedZone->getId() % ourCenter() % targetZone->getId() % targetZone->getCenter()() % maxDistance;
+				logGlobal->traceStream() << boost::format("direction is %s") % vec();
+
+				misplacedZone->setCenter(targetZone->getCenter() - vec.unitVector() * newDistanceBetweenZones); //zones should now overlap by half size
+				logGlobal->traceStream() << boost::format("New distance %f") % targetZone->getCenter().dist2d(misplacedZone->getCenter());
+			}
 		}
 		else
 		{