Fix ConversationAdapterTest#testGetItemIdEquals()

Regression introduced at cb670d67

Fixes #6652
Closes #6779
// FREEBIE

test/unitTest/java/org/thoughtcrime/securesms/ConversationAdapterTest.java

@@ -25,12 +25,12 @@ public class ConversationAdapterTest extends BaseUnitTest {
 
   @Test
   public void testGetItemIdEquals() throws Exception {
-    when(cursor.getString(anyInt())).thenReturn("SMS::1::1");
+    when(cursor.getString(anyInt())).thenReturn(null).thenReturn("SMS::1::1");
     long firstId = adapter.getItemId(cursor);
-    when(cursor.getString(anyInt())).thenReturn("MMS::1::1");
+    when(cursor.getString(anyInt())).thenReturn(null).thenReturn("MMS::1::1");
     long secondId = adapter.getItemId(cursor);
     assertNotEquals(firstId, secondId);
-    when(cursor.getString(anyInt())).thenReturn("MMS::2::1");
+    when(cursor.getString(anyInt())).thenReturn(null).thenReturn("MMS::2::1");
     long thirdId = adapter.getItemId(cursor);
     assertNotEquals(secondId, thirdId);
   }