Fix call to Vector & PODVector::EraseSwap(). Closes #1855.

Source/Urho3D/Container/Vector.h

@@ -340,7 +340,7 @@ public:
         Iterator i = Find(value);
         if (i != End())
         {
-            EraseSwap(i);
+            EraseSwap(i - Begin());
             return true;
         }
         else
@@ -914,7 +914,7 @@ public:
         Iterator i = Find(value);
         if (i != End())
         {
-            EraseSwap(i);
+            EraseSwap(i - Begin());
             return true;
         }
         else