remove mistaken assert

It's ok to fail to open a game, as will happen e.g. when a message
arrives for a game that was recently deleted.

xwords4/android/app/src/main/java/org/eehouse/android/xw4/DBUtils.java

@@ -1125,7 +1125,6 @@ public class DBUtils {
             }
             setCached( rowid, result );
         }
-        Assert.assertTrueNR( null != result );
         return result;
     }