remove comment and add {}

Author: MoseyQAQ

src/integrate/ensemble_mttk.cu

@@ -110,8 +110,9 @@ Ensemble_MTTK::Ensemble_MTTK(const char** params, int num_params)
     } else if (strcmp(params[i], "pperiod") == 0) {
       if (!is_valid_real(params[i + 1], &p_period[0][0]))
         PRINT_INPUT_ERROR("Wrong inputs for pperiod keyword.");
-      if (p_period[0][0] < 200) // Fix issue #1117
+      if (p_period[0][0] < 200) {
         PRINT_INPUT_ERROR("pperiod should >= 200 timestep."); 
+      }
       i += 2;
       for (int i = 0; i < 3; i++) {
         for (int j = 0; j < 3; j++) {