Bugfix: Material should be set to PhysicsMaterial::sDefault instead of null

Jolt/Physics/Character/CharacterBase.cpp

@@ -38,7 +38,7 @@ void CharacterBase::RestoreState(StateRecorder &inStream)
 	inStream.Read(mGroundNormal);
 	inStream.Read(mGroundVelocity);
 	mGroundUserData = 0; // Cannot restore user data
-	mGroundMaterial = nullptr; // Cannot restore material
+	mGroundMaterial = PhysicsMaterial::sDefault; // Cannot restore material
 }
 
 JPH_NAMESPACE_END

Jolt/Physics/Character/CharacterVirtual.cpp

@@ -1339,7 +1339,7 @@ void CharacterVirtual::Contact::RestoreState(StateRecorder &inStream)
 	inStream.Read(mWasDiscarded);
 	inStream.Read(mCanPushCharacter);
 	mUserData = 0; // Cannot restore user data
-	mMaterial = nullptr; // Cannot restore material
+	mMaterial = PhysicsMaterial::sDefault; // Cannot restore material
 }
 
 void CharacterVirtual::SaveState(StateRecorder &inStream) const