fix: fix a crash when placing a SIP call

The app crashed when placing a SIP call because ther was a wrong
check on account username

Change-Id: Ie9c1a2d83975150c5315bb4cba06e0b8836d7c92

ring-android/libringclient/src/main/java/cx/ring/call/CallPresenter.java

@@ -333,7 +333,7 @@ public class CallPresenter extends RootPresenter<CallView> implements Observer<S
         }
 
         String[] split = mSipCall.getNumber().split(":");
-        if (split.length > 0) {
+        if (split.length > 1) {
             mBlockchainInputHandler.enqueueNextLookup(split[1]);
         }
     }