Check the file size before closing the file

TNetXNGFile requires the file to be open to be able to run any size
checks

src/TJAlienFile.cxx

@@ -503,9 +503,6 @@ void TJAlienFile::Close(Option_t * option)
 {
     if (!IsOpen()) return;
 
-    // Close file
-    TAliceFile::Close(option);
-
     // If READ operation we can exit
     if (fOption == "READ")
         return;
@@ -514,6 +511,10 @@ void TJAlienFile::Close(Option_t * option)
     TString command("commit");
 
     Long64_t siz = GetSize();
+
+    // Close file
+    TAliceFile::Close(option);
+
     if (siz <= 0) {
         Error("Close", "the reported size of the written file is <= 0");
         return;