Merge branch 'master' into kimkulling/close_memleak-issue-3416

- closes https://github.com/assimp/assimp/issues/3416

include/assimp/MemoryIOWrapper.h

@@ -2,8 +2,7 @@
 Open Asset Import Library (assimp)
 ----------------------------------------------------------------------
 
-Copyright (c) 2006-2022, assimp team
-
+Copyright (c) 2006-2023, assimp team
 
 All rights reserved.
 
@@ -66,11 +65,7 @@ namespace Assimp    {
 // ----------------------------------------------------------------------------------
 class MemoryIOStream : public IOStream {
 public:
-    MemoryIOStream (const uint8_t* buff, size_t len, bool own = false)
-    : buffer (buff)
-    , length(len)
-    , pos((size_t)0)
-    , own(own) {
+    MemoryIOStream (const uint8_t* buff, size_t len, bool own = false) : buffer (buff), length(len), pos((size_t)0), own(own) {
         // empty
     }
 
@@ -162,7 +157,11 @@ public:
     }
 
     /** Destructor. */
-    ~MemoryIOSystem() = default;
+    ~MemoryIOSystem() {
+        for (auto &it : created_streams) {
+            delete it;
+        }
+    }
 
     // -------------------------------------------------------------------
     /** Tests for the existence of a file at the given path. */
@@ -176,18 +175,22 @@ public:
     // -------------------------------------------------------------------
     /** Returns the directory separator. */
     char getOsSeparator() const override {
-        return existing_io ? existing_io->getOsSeparator()
-                           : '/';  // why not? it doesn't care
+        return existing_io ? existing_io->getOsSeparator() : '/'; 
     }
 
     // -------------------------------------------------------------------
-    /** Open a new file with a given path. */
+    /// Open a new file with a given path.
     IOStream* Open(const char* pFile, const char* pMode = "rb") override {
+        if (pFile == nullptr) {
+            return nullptr;
+        }
+        
         if ( 0 == strncmp( pFile, AI_MEMORYIO_MAGIC_FILENAME, AI_MEMORYIO_MAGIC_FILENAME_LENGTH ) ) {
             created_streams.emplace_back(new MemoryIOStream(buffer, length));
             return created_streams.back();
         }
-        return existing_io ? existing_io->Open(pFile, pMode) : NULL;
+        
+        return existing_io ? existing_io->Open(pFile, pMode) : nullptr;
     }
 
     // -------------------------------------------------------------------