use braced delete where appropriate (#4984)

src/c_api.cpp

@@ -1966,17 +1966,17 @@ int LGBM_BoosterPredictSparseOutput(BoosterHandle handle,
 int LGBM_BoosterFreePredictSparse(void* indptr, int32_t* indices, void* data, int indptr_type, int data_type) {
   API_BEGIN();
   if (indptr_type == C_API_DTYPE_INT32) {
-    delete reinterpret_cast<int32_t*>(indptr);
+    delete[] reinterpret_cast<int32_t*>(indptr);
   } else if (indptr_type == C_API_DTYPE_INT64) {
-    delete reinterpret_cast<int64_t*>(indptr);
+    delete[] reinterpret_cast<int64_t*>(indptr);
   } else {
     Log::Fatal("Unknown indptr type in LGBM_BoosterFreePredictSparse");
   }
-  delete indices;
+  delete[] indices;
   if (data_type == C_API_DTYPE_FLOAT32) {
-    delete reinterpret_cast<float*>(data);
+    delete[] reinterpret_cast<float*>(data);
   } else if (data_type == C_API_DTYPE_FLOAT64) {
-    delete reinterpret_cast<double*>(data);
+    delete[] reinterpret_cast<double*>(data);
   } else {
     Log::Fatal("Unknown data type in LGBM_BoosterFreePredictSparse");
   }