3583195f85049bbf3dde8d15b3768617bc8183af Fix: An error would occur if…

… an export button was used as a split

https://datatables.net/forums/discussion/79944

Sync to source repo @3583195f85049bbf3dde8d15b3768617bc8183af

datatables.json

@@ -14,5 +14,5 @@
     ],
     "src-repo": "http://github.com/DataTables/Buttons",
     "last-tag": "3.1.2",
-    "last-sync": "6afc3b4246898c1cb56eb0fc5ff0f1837610309c"
+    "last-sync": "3583195f85049bbf3dde8d15b3768617bc8183af"
 }