Fix corner case of indexDates'

It's not enough to check that the list is empty, we also need to check
that we have some data to begin with, i.e. we need to skip calling
`toFstDate` or `toLstDate` if we have a list of empty strings.

src/Gargantext/Core/Viz/Phylo/PhyloMaker.hs

@@ -241,10 +241,10 @@ clusterToGroup fis pId pId' lvl idx coocs rootsCount = PhyloGroup pId pId' lvl i
 indexDates' :: Map (Date,Date) [Document] -> Map (Date,Date) (Text,Text)
 indexDates' m = map (\docs ->
   let ds = map (\d -> date' d) docs
-      f = if (null ds)
+      f = if (null ds || all T.null ds)
             then ""
             else toFstDate ds
-      l = if (null ds)
+      l = if (null ds || all T.null ds)
             then ""
             else toLstDate ds
    in (f,l)) m

src/Gargantext/Core/Viz/Phylo/PhyloTools.hs

@@ -30,7 +30,6 @@ import Data.Vector (Vector, elemIndex)
 import Data.Vector qualified as Vector
 import Gargantext.Core.Viz.Phylo
 import Gargantext.Prelude hiding (empty)
-import Prelude (read)
 import Text.Printf
 
 ------------
@@ -160,7 +159,7 @@ toFstDate ds = snd
              $ head' "firstDate"
              $ sortOn fst
              $ map (\d ->
-                      let d' = read (filter (\c -> notElem c ['U','T','C',' ',':','-']) $ unpack d)::Int
+                      let d' = fromMaybe (error "toFstDate") $ readMaybe (filter (\c -> notElem c ['U','T','C',' ',':','-']) $ unpack d)::Int
                        in (d',d)) ds
 
 toLstDate :: [Text] -> Text
@@ -169,7 +168,7 @@ toLstDate ds = snd
              $ reverse
              $ sortOn fst
              $ map (\d ->
-                      let d' = read (filter (\c -> notElem c ['U','T','C',' ',':','-']) $ unpack d)::Int
+                      let d' = fromMaybe (error "toLstDate") $ readMaybe (filter (\c -> notElem c ['U','T','C',' ',':','-']) $ unpack d)::Int
                        in (d',d)) ds