fix SHFileOperation in FileSystem::DeleteDir

gframe/myfilesystem.h

@@ -18,6 +18,7 @@
 
 #define NOMINMAX
 #include <Windows.h>
+#include <shellapi.h>
 
 class FileSystem {
 public:
@@ -71,13 +72,18 @@ public:
 	}
 
 	static bool DeleteDir(const wchar_t* wdir) {
-		wchar_t pdir[256];
+		size_t len = std::wcslen(wdir);
+		wchar_t pdir[1024 + 1]{};
+		if(len >= 1024)
+			return false;
 		BufferIO::CopyWideString(wdir, pdir);
+		// pFrom must be double-null terminated for SHFileOperationW
+		// pdir[len] is already '\0' and pdir[len+1] is '\0' due to zero-init
 		SHFILEOPSTRUCTW lpFileOp{};
 		lpFileOp.hwnd = nullptr;
 		lpFileOp.wFunc = FO_DELETE;
 		lpFileOp.pFrom = pdir;
-		lpFileOp.pTo = 0;
+		lpFileOp.pTo = nullptr;
 		lpFileOp.fFlags = FOF_ALLOWUNDO | FOF_NOCONFIRMATION | FOF_NOERRORUI | FOF_SILENT;
 		return SHFileOperationW(&lpFileOp) == 0;
 	}