Merge branch 'check_pathgrid' into 'master'

Make sure PathFinder::getClosestPoint is not called with failing precondition (#6294)

Closes #6294

See merge request OpenMW/openmw!1236

apps/openmw/mwmechanics/aicombat.cpp

@@ -348,7 +348,7 @@ namespace MWMechanics
 
                         bool runFallback = true;
 
-                        if (pathgrid && !actor.getClass().isPureWaterCreature(actor))
+                        if (pathgrid != nullptr && !pathgrid->mPoints.empty() && !actor.getClass().isPureWaterCreature(actor))
                         {
                             ESM::Pathgrid::PointList points;
                             Misc::CoordinateConverter coords(storage.mCell->getCell());

apps/openmw/mwmechanics/aiwander.cpp

@@ -758,6 +758,9 @@ namespace MWMechanics
         const ESM::Pathgrid *pathgrid =
             MWBase::Environment::get().getWorld()->getStore().get<ESM::Pathgrid>().search(*currentCell->getCell());
 
+        if (pathgrid == nullptr || pathgrid->mPoints.empty())
+            return;
+
         int index = PathFinder::getClosestPoint(pathgrid, PathFinder::makeOsgVec3(dest));
 
         getPathGridGraph(currentCell).getNeighbouringPoints(index, points);