Rearrange init some to fix a crash, details:

mr was not being intialized before it was being used by the stepper intialization.

Also added a check to prevent it from happening from other places.

g2core/main.cpp

@@ -100,11 +100,11 @@ void application_init_machine(void)
 {
     cm = &cm1;                          // set global canonical machine pointer to primary machine
     cm->machine_state = MACHINE_INITIALIZING;
+    canonical_machine_inits();          // combined inits for CMs and planner - do before anything might use cm or mr!
 
     stepper_init();                     // stepper subsystem
     encoder_init();                     // virtual encoders
     gpio_init();                        // inputs and outputs
-    canonical_machine_inits();          // combined inits for CMs and planner
 }
 
 void application_init_startup(void)

g2core/planner.cpp

@@ -264,6 +264,12 @@ void mp_set_runtime_position(uint8_t axis, const float position) { mr->position[
 
 void mp_set_steps_to_runtime_position()
 {
+    if (mr == nullptr) {
+#if IN_DEBUGGER
+        __asm__ volatile("BKPT 1"); // mp_set_steps_to_runtime_position called with null mr!
+#endif
+        return;
+    }
     float step_position[MOTORS];
     // There use to be a call to kn_inverse_kinematics here, but we don't do that now, instead we call kn->sync_encoders()
     // after handling the steps, allowing the kinematics to intelligently handle the offset of step and position.