Release memory allocated in constructors

Adafruit_SPIDevice.cpp

@@ -70,6 +70,14 @@ Adafruit_SPIDevice::Adafruit_SPIDevice(int8_t cspin, int8_t sckpin,
   _spi = NULL;
 }
 
+// release memory allocated in constructors
+Adafruit_SPIDevice::~Adafruit_SPIDevice() {
+  if (_spiSetting) {
+    delete _spiSetting;
+    _spiSetting = nullptr;
+  }
+}
+
 /*!
  *    @brief  Initializes SPI bus and sets CS pin high
  *    @return Always returns true because there's no way to test success of SPI

Adafruit_SPIDevice.h

@@ -64,6 +64,7 @@ public:
                      uint32_t freq = 1000000,
                      BitOrder dataOrder = SPI_BITORDER_MSBFIRST,
                      uint8_t dataMode = SPI_MODE0);
+  ~Adafruit_SPIDevice();
 
   bool begin(void);
   bool read(uint8_t *buffer, size_t len, uint8_t sendvalue = 0xFF);