Use NOT_A_DICT_POS instead of 0 to express not valid ditctionary position.

Bug: 6669677
Change-Id: I4bf2284f8221a0a2ae4534b4a06b0e59c420a5f9
diff --git a/native/jni/src/defines.h b/native/jni/src/defines.h
index e349aed..cb66814 100644
--- a/native/jni/src/defines.h
+++ b/native/jni/src/defines.h
@@ -270,6 +270,7 @@
 #define NOT_A_COORDINATE (-1)
 #define NOT_AN_INDEX (-1)
 #define NOT_A_PROBABILITY (-1)
+#define NOT_A_DICT_POS (S_INT_MIN)
 
 #define KEYCODE_SPACE ' '
 #define KEYCODE_SINGLE_QUOTE '\''