Merge pull request #86 from klarman-cell-observatory/yiming

Fix bug in write_dataframe of zarr_utils

pegasusio/zarr_utils.py

@@ -313,7 +313,7 @@ def write_dataframe(self, parent: zarr.Group, name: str, df: pd.DataFrame) -> No
         attrs_dict['index_name'] = df.index.name if df.index.name is not None else 'index'
         self.write_series(group, '_index', df.index.values)
         for col in df.columns:
-            if isinstance(df[col].values[0], PIL.Image.Image):
+            if (len(df[col]) != 0) and (isinstance(df[col].values[0], PIL.Image.Image)):
                 colgroup = group.create_group(col, overwrite = True)
                 x = 0
                 for data in df[col].values: