reading non'existing files from archives doesn't crash

Author: sadiuk

include/nbl/system/IFileArchive.h

@@ -135,6 +135,7 @@ class IFileArchive : public core::IReferenceCounted
 	core::smart_refctd_ptr<IFile> readFile(const SOpenFileParams& params)
 	{
 		auto index = getIndexByPath(params.filename);
+		if (index == -1) return nullptr;
 		switch (this->getFileType(index))
 		{
 		case EAT_NULL:

include/nbl/system/ISystem.h

@@ -181,7 +181,7 @@ class ISystem : public core::IReferenceCounted
             auto& params = std::get<IFileArchive::SOpenFileParams>(found);
             // TODO: support passwords
             auto f =  archive->readFile(params);
-            assert(f.get()); // cannot fail
+            //assert(f.get()); // cannot fail
             return f;
         }