Return empty string for null notes to avoid showing null in UI.

Change-Id: I1f60ce48d9d11b074aa268eda118c427b3cc62c0

android/sdremote/src/org/libreoffice/impressremote/communication/NetworkClient.java

@@ -56,6 +56,11 @@ public class NetworkClient extends Client {
         // Wait until we get the appropriate string back...
         String aTemp = mReader.readLine();
 
+        if (aTemp == null) {
+            throw new IOException(
+                            "End of stream reached before any data received.");
+        }
+
         while (!aTemp.equals("LO_SERVER_SERVER_PAIRED")) {
             if (aTemp.equals("LO_SERVER_VALIDATING_PIN")) {
                 // Broadcast that we need a pin screen.

android/sdremote/src/org/libreoffice/impressremote/communication/SlideShow.java

@@ -62,7 +62,12 @@ public class SlideShow {
     }
 
     public String getNotes(int aSlide) {
-        return mNotes.get(aSlide);
+        String aNote = mNotes.get(aSlide);
+        if (aNote != null) {
+            return aNote;
+        } else {
+            return "";
+        }
     }
 
     // ---------------------------------------------------- TIMER --------------