AP_RangeFinder: check I2C dev during detect

libraries/AP_RangeFinder/AP_RangeFinder_LightWareI2C.cpp

@@ -37,6 +37,10 @@ AP_RangeFinder_LightWareI2C::AP_RangeFinder_LightWareI2C(RangeFinder::RangeFinde
 */
 AP_RangeFinder_Backend *AP_RangeFinder_LightWareI2C::detect(RangeFinder::RangeFinder_State &_state, AP_HAL::OwnPtr<AP_HAL::I2CDevice> dev)
 {
+    if (!dev) {
+        return nullptr;
+    }
+
     AP_RangeFinder_LightWareI2C *sensor
         = new AP_RangeFinder_LightWareI2C(_state, std::move(dev));
 

libraries/AP_RangeFinder/AP_RangeFinder_MaxsonarI2CXL.cpp

@@ -51,6 +51,10 @@ AP_RangeFinder_MaxsonarI2CXL::AP_RangeFinder_MaxsonarI2CXL(RangeFinder::RangeFin
 AP_RangeFinder_Backend *AP_RangeFinder_MaxsonarI2CXL::detect(RangeFinder::RangeFinder_State &_state,
                                                              AP_HAL::OwnPtr<AP_HAL::I2CDevice> dev)
 {
+    if (!dev) {
+        return nullptr;
+    }
+
     AP_RangeFinder_MaxsonarI2CXL *sensor
         = new AP_RangeFinder_MaxsonarI2CXL(_state, std::move(dev));
     if (!sensor) {

libraries/AP_RangeFinder/AP_RangeFinder_TeraRangerI2C.cpp

@@ -49,6 +49,10 @@ AP_RangeFinder_TeraRangerI2C::AP_RangeFinder_TeraRangerI2C(RangeFinder::RangeFin
 AP_RangeFinder_Backend *AP_RangeFinder_TeraRangerI2C::detect(RangeFinder::RangeFinder_State &_state,
                                                              AP_HAL::OwnPtr<AP_HAL::I2CDevice> i2c_dev)
 {
+    if (!i2c_dev) {
+        return nullptr;
+    }
+
     AP_RangeFinder_TeraRangerI2C *sensor = new AP_RangeFinder_TeraRangerI2C(_state, std::move(i2c_dev));
     if (!sensor) {
         return nullptr;