fix clang compiler error in debug

optimizer/extlib/nsga2/nsga2.c

@@ -146,7 +146,7 @@ void write_flag(char* filename, int flag)
 {
      FILE *fp;
 
-     assert(0 <= flag <= 11);
+     assert(0 <= flag && flag <= 11);
      
      fp = fopen(filename, "w");
      assert(fp != NULL);