Don't throw an exception when equipping a bound item fails

CHANGELOG.md

@@ -112,6 +112,7 @@
     Bug #5899: Visible modal windows and dropdowns crashing game on exit
     Bug #5902: NiZBufferProperty is unable to disable the depth test
     Bug #5906: Sunglare doesn't work with Mesa drivers and AMD GPUs
+    Bug #5912: ImprovedBound mod doesn't work
     Feature #390: 3rd person look "over the shoulder"
     Feature #832: OpenMW-CS: Handle deleted references
     Feature #1536: Show more information about level on menu

apps/openmw/mwmechanics/actors.cpp

@@ -346,7 +346,11 @@ namespace MWMechanics
         if (actor != MWMechanics::getPlayer())
             return;
 
-        MWWorld::Ptr newItem = *store.getSlot(slot);
+        MWWorld::Ptr newItem;
+        auto it = store.getSlot(slot);
+        // Equip can fail because beast races cannot equip boots/helmets
+        if(it != store.end())
+            newItem = *it;
 
         if (newItem.isEmpty() || boundPtr != newItem)
             return;