prevent empty off target crash

tiger.py

@@ -223,10 +223,6 @@ def tiger_exhibit(transcripts: pd.DataFrame, status_bar=None, status_text=None,
     if option=='On and Off Target' and len(off_target_predictions) > 0:
         off_target_predictions['Guide'] = off_target_predictions['Guide'].apply(lambda s: s[::-1])
 
-    # reverse guide sequences
-    on_target_predictions['Guide'] = on_target_predictions['Guide'].apply(lambda s: s[::-1])
-    off_target_predictions['Guide'] = off_target_predictions['Guide'].apply(lambda s: s[::-1])
-
     return on_target_predictions.reset_index(drop=True), off_target_predictions.reset_index(drop=True)