added a null check for oauth1 signature calculating, now this class can be used to acquire request token within the oauth dance logic

Author: haed

api/src/main/java/org/asynchttpclient/oauth/OAuthSignatureCalculator.java

@@ -126,7 +126,9 @@ public String calculateSignature(String method, String baseURL, long oauthTimest
         allParameters.add(KEY_OAUTH_NONCE, nonce);
         allParameters.add(KEY_OAUTH_SIGNATURE_METHOD, OAUTH_SIGNATURE_METHOD);
         allParameters.add(KEY_OAUTH_TIMESTAMP, String.valueOf(oauthTimestamp));
-        allParameters.add(KEY_OAUTH_TOKEN, userAuth.getKey());
+        if (userAuth.getKey() != null) {
+            allParameters.add(KEY_OAUTH_TOKEN, userAuth.getKey());
+        }
         allParameters.add(KEY_OAUTH_VERSION, OAUTH_VERSION_1_0);
 
         if (formParams != null) {
@@ -164,7 +166,9 @@ public String constructAuthHeader(String signature, String nonce, long oauthTime
         StringBuilder sb = new StringBuilder(200);
         sb.append("OAuth ");
         sb.append(KEY_OAUTH_CONSUMER_KEY).append("=\"").append(consumerAuth.getKey()).append("\", ");
-        sb.append(KEY_OAUTH_TOKEN).append("=\"").append(userAuth.getKey()).append("\", ");
+        if (userAuth.getKey() != null) {
+            sb.append(KEY_OAUTH_TOKEN).append("=\"").append(userAuth.getKey()).append("\", ");
+        }
         sb.append(KEY_OAUTH_SIGNATURE_METHOD).append("=\"").append(OAUTH_SIGNATURE_METHOD).append("\", ");
 
         // careful: base64 has chars that need URL encoding: