Fix out of array bounds access.

Manifested as compiler warnings:

In file included from sketch/Marlin_main.cpp:67:0:
sketch/temperature.h: In function 'bool gcode_M45(bool, int8_t)':
sketch/temperature.h:142:30: warning: array subscript is above array bounds [-Warray-bounds]
   target_temperature[extruder] = celsius;
                              ^
sketch/temperature.h:142:30: warning: array subscript is above array bounds [-Warray-bounds]
   target_temperature[extruder] = celsius;
                              ^
sketch/temperature.h: In function 'void long_pause()':
sketch/temperature.h:142:30: warning: array subscript is above array bounds [-Warray-bounds]
   target_temperature[extruder] = celsius;
                              ^
sketch/temperature.h:142:30: warning: array subscript is above array bounds [-Warray-bounds]
   target_temperature[extruder] = celsius;
                              ^
sketch/temperature.h: In function 'void process_commands()':
sketch/temperature.h:142:30: warning: array subscript is above array bounds [-Warray-bounds]
   target_temperature[extruder] = celsius;
                              ^
sketch/temperature.h:142:30: warning: array subscript is above array bounds [-Warray-bounds]
   target_temperature[extruder] = celsius;
                              ^

Firmware/Marlin_main.cpp

@@ -1780,7 +1780,7 @@ int chunkHead = 0;
 
 void serial_read_stream() {
 
-    setTargetHotend(0, 0);
+    setAllTargetHotends(0);
     setTargetBed(0);
 
     lcd_clear();
@@ -2874,9 +2874,7 @@ bool gcode_M45(bool onlyZ, int8_t verbosity_level)
 	if (!onlyZ)
 	{
 		setTargetBed(0);
-		setTargetHotend(0, 0);
-		setTargetHotend(0, 1);
-		setTargetHotend(0, 2);
+		setAllTargetHotends(0);
 		adjust_bed_reset(); //reset bed level correction
 	}
 
@@ -5262,7 +5260,10 @@ Sigma_Exit:
       if(setTargetedHotend(104)){
         break;
       }
-      if (code_seen('S')) setTargetHotend(code_value(), tmp_extruder);
+      if (code_seen('S'))
+      {
+          setTargetHotendSafe(code_value(), tmp_extruder);
+      }
       setWatch();
       break;
     case 112: //  M112 -Emergency Stop
@@ -5375,10 +5376,10 @@ Sigma_Exit:
         autotemp_enabled=false;
       #endif
       if (code_seen('S')) {
-        setTargetHotend(code_value(), tmp_extruder);
+          setTargetHotendSafe(code_value(), tmp_extruder);
               CooldownNoWait = true;
             } else if (code_seen('R')) {
-              setTargetHotend(code_value(), tmp_extruder);
+                setTargetHotendSafe(code_value(), tmp_extruder);
         CooldownNoWait = false;
       }
       #ifdef AUTOTEMP
@@ -6366,9 +6367,7 @@ bFirst=false;
 				if (millis() > waiting_start_time + (unsigned long)M600_TIMEOUT * 1000) {
 					lcd_display_message_fullscreen_P(_i("Press knob to preheat nozzle and continue."));////MSG_PRESS_TO_PREHEAT c=20 r=4
 					wait_for_user_state = 1;
-					setTargetHotend(0, 0);
-					setTargetHotend(0, 1);
-					setTargetHotend(0, 2);
+					setAllTargetHotends(0);
 					st_synchronize();
 					disable_e0();
 					disable_e1();
@@ -7508,7 +7507,7 @@ static void handleSafetyTimer()
     else if (safetyTimer.expired(safetytimer_inactive_time))
     {
         setTargetBed(0);
-        setTargetHotend(0, 0);
+        setAllTargetHotends(0);
         lcd_show_fullscreen_message_and_wait_P(_i("Heating disabled by safety timer."));////MSG_BED_HEATING_SAFETY_DISABLED c=0 r=0
     }
 }
@@ -8313,9 +8312,7 @@ void long_pause() //long pause print
 	plan_buffer_line(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS], current_position[E_AXIS], 15, active_extruder);
 
 	//set nozzle target temperature to 0
-	setTargetHotend(0, 0);
-	setTargetHotend(0, 1);
-	setTargetHotend(0, 2);
+	setAllTargetHotends(0);
 
 	//Move XY to side
 	current_position[X_AXIS] = X_PAUSE_POS;

Firmware/temperature.cpp

@@ -1373,8 +1373,7 @@ void temp_runaway_stop(bool isPreheat, bool isBed)
 
 void disable_heater()
 {
-  for(int i=0;i<EXTRUDERS;i++)
-    setTargetHotend(0,i);
+  setAllTargetHotends(0);
   setTargetBed(0);
   #if defined(TEMP_0_PIN) && TEMP_0_PIN > -1
   target_temperature[0]=0;

Firmware/temperature.h

@@ -142,6 +142,16 @@ FORCE_INLINE void setTargetHotend(const float &celsius, uint8_t extruder) {
   target_temperature[extruder] = celsius;
 };
 
+static inline void setTargetHotendSafe(const float &celsius, uint8_t extruder)
+{
+    if (extruder<EXTRUDERS) target_temperature[extruder] = celsius;
+}
+
+static inline void setAllTargetHotends(const float &celsius)
+{
+    for(int i=0;i<EXTRUDERS;i++) setTargetHotend(celsius,i);
+}
+
 FORCE_INLINE void setTargetBed(const float &celsius) {  
   target_temperature_bed = celsius;
 };

Firmware/ultralcd.cpp

@@ -1804,9 +1804,7 @@ void lcd_commands()
 			cancel_heatup = true;
 			setTargetBed(0);
 			#if !(defined (SNMM) || defined (SNMM_V2))
-			setTargetHotend(0, 0);	//heating when changing filament for multicolor
-			setTargetHotend(0, 1);
-			setTargetHotend(0, 2);
+			setAllTargetHotends(0);
 			#endif
 			manage_heater();
 			custom_message = true;
@@ -2036,9 +2034,7 @@ void lcd_preheat_flex()
 
 void lcd_cooldown()
 {
-  setTargetHotend0(0);
-  setTargetHotend1(0);
-  setTargetHotend2(0);
+  setAllTargetHotends(0);
   setTargetBed(0);
   fanSpeed = 0;
   lcd_return_to_status();
@@ -3126,7 +3122,7 @@ void lcd_adjust_z() {
 
 bool lcd_wait_for_pinda(float temp) {
 	lcd_set_custom_characters_degree();
-	setTargetHotend(0, 0);
+	setAllTargetHotends(0);
 	setTargetBed(0);
 	LongTimer pinda_timeout;
 	pinda_timeout.start();
@@ -3166,7 +3162,7 @@ void lcd_wait_for_heater() {
 
 void lcd_wait_for_cool_down() {
 	lcd_set_custom_characters_degree();
-	setTargetHotend(0,0);
+	setAllTargetHotends(0);
 	setTargetBed(0);
 	while ((degHotend(0)>MAX_HOTEND_TEMP_CALIBRATION) || (degBed() > MAX_BED_TEMP_CALIBRATION)) {
 		lcd_display_message_fullscreen_P(_i("Waiting for nozzle and bed cooling"));////MSG_WAITING_TEMP c=20 r=3