Reorder init to supress warnings

src/COMPRESS/zstd_file_writer.cpp

@@ -24,10 +24,10 @@
 using namespace LAMMPS_NS;
 
 ZstdFileWriter::ZstdFileWriter() : FileWriter(),
-    fp(nullptr),
-    cctx(nullptr),
     compression_level(0),
-    checksum_flag(1)
+    checksum_flag(1),
+    cctx(nullptr),
+    fp(nullptr)
 {
   out_buffer_size = ZSTD_CStreamOutSize();
   out_buffer = new char[out_buffer_size];