text messages: don't send if empty

Tuleap: #123
Change-Id: I70af840996fb6f7b78a863a90de39f10eedcb7b2

ring-android/app/src/main/java/cx/ring/client/ConversationActivity.java

@@ -193,8 +193,11 @@ public class ConversationActivity extends AppCompatActivity {
             public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {
                 switch (actionId) {
                     case EditorInfo.IME_ACTION_SEND:
+                        CharSequence txt = msgEditTxt.getText();
+                        if (txt.length() > 0) {
                             onSendTextMessage(msgEditTxt.getText().toString());
                             msgEditTxt.setText("");
+                        }
                         return true;
                 }
                 return false;
@@ -204,9 +207,12 @@ public class ConversationActivity extends AppCompatActivity {
         msgSendBtn.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View v) {
-                onSendTextMessage(msgEditTxt.getText().toString());
+                CharSequence txt = msgEditTxt.getText();
+                if (txt.length() > 0) {
+                    onSendTextMessage(txt.toString());
                     msgEditTxt.setText("");
                 }
+            }
         });
         bottomPane = (ViewGroup) findViewById(R.id.ongoingcall_pane);
         bottomPane.setVisibility(View.GONE);