check for updates in dI data

code/UNFCCC_DI_reader/UNFCCC_DI_reader_core.py

@@ -394,7 +394,7 @@ def convert_DI_IF_data_to_pm2(
 )-> xr.Dataset:
     if_index_cols = set(itertools.chain(*data_di_if.attrs["dimensions"].values()))
     time_cols = set(data_di_if.columns.values) - if_index_cols
-    data_di_if.dropna(subset=time_cols, inplace=True)
+    data_di_if.dropna(subset=time_cols, inplace=True, how="all")
 
     #try:
         # try to convert all in one go

datasets/UNFCCC/no_updates_until.txt

@@ -0,0 +1,3 @@
+22/08/30: data is identical to 22/08/22
+22/09/26: data is identical to 22/08/22
+