Merge pull request #351 from pythagorasw/fix-due-tryAllocateQueue

samx3-due: Fix null result from tryAllocateQueue()

Author: gin66

src/pd_sam/sam_queue.h

@@ -8,7 +8,7 @@ class StepperQueue : public StepperQueueBase {
  public:
 #include "../fas_queue/protocol.h"
 
-  uint8_t _step_pin;
+  uint8_t _step_pin = PIN_UNDEFINED;
   uint8_t _queue_num;
   void* driver_data;
   volatile bool _hasISRactive;