Correct HOTENDS for SWITCHING_EXTRUDER

Marlin/src/module/stepper.cpp

@@ -1841,10 +1841,8 @@ uint32_t Stepper::stepper_block_phase_isr() {
         current_adv_steps++;
         interval = eISR_Rate;
       }
-      else {
-        interval = ADV_NEVER;
-        eISR_Rate = ADV_NEVER;
-      }
+      else
+        interval = eISR_Rate = ADV_NEVER;
     }
     else
       interval = ADV_NEVER;

Marlin/src/module/temperature.h

@@ -42,6 +42,12 @@
   #define SOFT_PWM_SCALE 0
 #endif
 
+#if HOTENDS == 1
+  #define HOTEND_INDEX  0
+#else
+  #define HOTEND_INDEX  e
+#endif
+
 /**
  * States for ADC reading in the ISR
  */