error msg change and getAttribute() change

Author: Han Chen

src/main/java/com/onelogin/saml/Response.java

@@ -76,7 +76,7 @@ public void loadXmlFromBase64(String responseStr) throws Exception {
 		this.response = new String(decodedB);
 		this.document = Utils.loadXML(this.response);
 		if(this.document == null){
-			throw new Exception("SAML Response could not be processed");
+			throw new Exception("SAML Response could not be processed, invalid or empty SAML");
 		}
 	}
 
@@ -253,8 +253,10 @@ public String getNameId() throws Exception {
 
 	public String getAttribute(String name) {
 		HashMap<String, ArrayList<String>> attributes = getAttributes();
+
 		if (!attributes.isEmpty()) {
-			return attributes.get(name).toString();
+			ArrayList<String> attrVal = attributes.get(name);
+            return attrVal == null || attrVal.size() == 0 ? null : attrVal.get(0).toString();
 		}
 		return null;
 	}