Fix stability test

silk/tests/test_unit_LPC_inv_pred_gain.c

@@ -77,7 +77,7 @@ int check_stability(opus_int16 *A_Q12, int order) {
         if( ( i & 0x7 ) == 0 ) {
             double amp = 0;
             for( j = 0; j < order; j++ ) {
-                amp += fabs(y[0]);
+                amp += fabs(y[j]);
             }
             if( amp < 0.00001 ) {
                 return 1;