DroidFish: Avoid crash if asked to speak a null move.

DroidFish/src/org/petero/droidfish/Speech.java

@@ -145,7 +145,7 @@ public class Speech {
 
     /** Convert move "move" in position "pos" to a sentence that can be spoken. */
     public static String moveToText(Position pos, Move move, Language lang) {
-        if (move == null)
+        if (move == null || move.from == move.to)
             return "";
 
         String moveStr = TextIO.moveToString(pos, move, false, false);

DroidFishTest/src/org/petero/droidfish/gamelogic/SpeechTest.java

@@ -206,6 +206,8 @@ public class SpeechTest extends TestCase {
             Pair<Boolean,Move> res = game.processString("Nexc3");
             assertEquals(new String[]{"Knight e takes, c3", "Springer e schlägt c3", "Caballo e captura c3"},
                     moveToText(game.prevPos(), res.second, lang));
+            assertEquals(new String[]{"", "", ""},
+                    moveToText(game.prevPos(), new Move(0, 0, 0), lang));
         }
     }