message: Fix for get creds for proof request for edge cases
diff: @@ -163,6 +163,11 @@ pub fn libindy_prover_get_credentials_for_proof_req(proof_req: &str) -> VcxResul
  }).ok()
  });
  + // handle special case of "empty because json is bad" vs "empty because no attributes sepected"
  + if requested_attributes == None && requested_predicates == None {
  + return Err(VcxError::from_msg(VcxErrorKind::InvalidAttributesStructure, "Invalid Json Parsing of Requested Attributes Retrieved From Libindy"));
  + }
  +
  let mut fetch_attrs: Map<String, Value> = match requested_attributes {
  Some(attrs) => attrs.clone(),
  None => Map::new()
  @@ -185,7 +190,7 @@ pub fn libindy_prover_get_credentials_for_proof_req(proof_req: &str) -> VcxResul
  let _ = close_search_handle(search_handle);
  Ok(creds)
  } else {
  - Err(VcxError::from_msg(VcxErrorKind::InvalidAttributesStructure, "Invalid Json Parsing of Requested Attributes Retrieved From Libindy"))
  + Ok("{}".to_string())
  }
  }
  