added test to travel all links

rowers/dataprep.py

@@ -309,6 +309,8 @@ def clean_df_stats(datadf, workstrokesonly=True, ignorehr=True,
     # clean data remove zeros and negative values
 
     # bring metrics which have negative values to positive domain
+    if datadf.empty:
+        return datadf
     try:
         datadf['catch'] = -datadf['catch']
     except KeyError:
@@ -1670,7 +1672,7 @@ def getsmallrowdata_db(columns, ids=[], doclean=True, workstrokesonly=True):
 
         try:
             f = row.df['TimeStamp (sec)'].diff().mean()
-        except AttributeError:
+        except (AttributeError,KeyError) as e:
             f = 0
             
         if f != 0 and not np.isnan(f):