Opus: Ensure that NLSF cannot be negative when computing a min distance between them

third_party/opus/src/silk/NLSF_stabilize.c

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@@ skipping 112 matching lines @@
         /* Insertion sort (fast for already almost sorted arrays):   */
         /* Best case:  O(n)   for an already sorted array            */
         /* Worst case: O(n^2) for an inversely sorted array          */
         silk_insertion_sort_increasing_all_values_int16( &NLSF_Q15[0], L );
 
         /* First NLSF should be no less than NDeltaMin[0] */
         NLSF_Q15[0] = silk_max_int( NLSF_Q15[0], NDeltaMin_Q15[0] );
 
         /* Keep delta_min distance between the NLSFs */
         for( i = 1; i < L; i++ )
-            NLSF_Q15[i] = silk_max_int( NLSF_Q15[i], NLSF_Q15[i-1] + NDeltaMin_Q15[i] );
+            NLSF_Q15[i] = silk_max_int( NLSF_Q15[i], silk_ADD_SAT16( NLSF_Q15[i-1], NDeltaMin_Q15[i] ) );
 
         /* Last NLSF should be no higher than 1 - NDeltaMin[L] */
         NLSF_Q15[L-1] = silk_min_int( NLSF_Q15[L-1], (1<<15) - NDeltaMin_Q15[L] );
 
         /* Keep NDeltaMin distance between the NLSFs */
         for( i = L-2; i >= 0; i-- )
             NLSF_Q15[i] = silk_min_int( NLSF_Q15[i], NLSF_Q15[i+1] - NDeltaMin_Q15[i+1] );
     }
 }