Fix issues with model data storage when doing long actions in async (eg. SDF generation)

Source/Engine/Content/Storage/FlaxStorage.cpp

@@ -75,8 +75,6 @@ FlaxChunk* FlaxChunk::Clone() const
 
 const int32 FlaxStorage::MagicCode = 1180124739;
 
-FlaxStorage::LockData FlaxStorage::LockData::Invalid(nullptr);
-
 struct Header
 {
     int32 MagicCode;

Source/Engine/Content/Storage/FlaxStorage.h

@@ -146,7 +146,6 @@ public:
     struct LockData
     {
         friend FlaxStorage;
-        static LockData Invalid;
 
     private:
         FlaxStorage* _storage;
@@ -159,6 +158,11 @@ public:
         }
 
     public:
+        LockData()
+            : _storage(nullptr)
+        {
+        }
+
         LockData(const LockData& other)
             : _storage(other._storage)
         {