[graph] fix snapshot by adding empty children to node

src/Gargantext/Components/GraphExplorer/Types.purs

@@ -18,12 +18,13 @@ type GraphId = Int
 
 newtype Node = Node {
     attributes :: Cluster
-  , id_ :: String
-  , label :: String
-  , size :: Int
-  , type_ :: String
-  , x :: Number
-  , y :: Number
+  , children   :: Array String
+  , id_        :: String
+  , label      :: String
+  , size       :: Int
+  , type_      :: String
+  , x          :: Number
+  , y          :: Number
   }
 
 x_coordP = SProxy :: SProxy "x_coord"

src/Gargantext/Components/GraphExplorer/Utils.purs

@@ -15,6 +15,7 @@ stEdgeToGET { _original } = _original
 stNodeToGET :: Record ST.Node -> GET.Node
 stNodeToGET { id, label, x, y, _original: GET.Node { attributes, size, type_ } } = GET.Node {
     attributes
+  , children: []
   , id_: id
   , label
   , size