Fix: Thermal runaway if nonexistent bed's temp is set

Marlin/Conditionals_post.h

 
   #define HAS_THERMALLY_PROTECTED_BED (HAS_TEMP_BED && HAS_HEATER_BED && ENABLED(THERMAL_PROTECTION_BED))
 
+  #define WATCH_HOTENDS (ENABLED(THERMAL_PROTECTION_HOTENDS) && WATCH_TEMP_PERIOD > 0)
+  #define WATCH_THE_BED (HAS_THERMALLY_PROTECTED_BED && WATCH_BED_TEMP_PERIOD > 0)
+
   /**
    * This setting is also used by M109 when trying to calculate
    * a ballpark safe margin to prevent wait-forever situation.

Marlin/temperature.cpp

   volatile int Temperature::babystepsTodo[XYZ] = { 0 };
 #endif
 
-#if ENABLED(THERMAL_PROTECTION_HOTENDS) && WATCH_TEMP_PERIOD > 0
+#if WATCH_HOTENDS
   int Temperature::watch_target_temp[HOTENDS] = { 0 };
   millis_t Temperature::watch_heater_next_ms[HOTENDS] = { 0 };
 #endif
 
-#if ENABLED(THERMAL_PROTECTION_BED) && WATCH_BED_TEMP_PERIOD > 0
+#if WATCH_THE_BED
   int Temperature::watch_target_bed_temp = 0;
   millis_t Temperature::watch_bed_next_ms = 0;
 #endif
     if (current_temperature[0] < max(HEATER_0_MINTEMP, MAX6675_TMIN + 0.01)) min_temp_error(0);
   #endif
 
-  #if (ENABLED(THERMAL_PROTECTION_HOTENDS) && WATCH_TEMP_PERIOD > 0) || (ENABLED(THERMAL_PROTECTION_BED) && WATCH_BED_TEMP_PERIOD > 0) || DISABLED(PIDTEMPBED) || HAS_AUTO_FAN
+  #if WATCH_HOTENDS || WATCH_THE_BED || DISABLED(PIDTEMPBED) || HAS_AUTO_FAN
     millis_t ms = millis();
   #endif
 
     soft_pwm[e] = (current_temperature[e] > minttemp[e] || is_preheating(e)) && current_temperature[e] < maxttemp[e] ? (int)pid_output >> 1 : 0;
 
     // Check if the temperature is failing to increase
-    #if ENABLED(THERMAL_PROTECTION_HOTENDS) && WATCH_TEMP_PERIOD > 0
+    #if WATCH_HOTENDS
 
       // Is it time to check this extruder's heater?
       if (watch_heater_next_ms[e] && ELAPSED(ms, watch_heater_next_ms[e])) {
     #endif // THERMAL_PROTECTION_HOTENDS
 
     // Check if the temperature is failing to increase
-    #if ENABLED(THERMAL_PROTECTION_BED) && WATCH_BED_TEMP_PERIOD > 0
+    #if WATCH_THE_BED
 
       // Is it time to check the bed?
       if (watch_bed_next_ms && ELAPSED(ms, watch_bed_next_ms)) {
   #endif //BED_MAXTEMP
 }
 
-#if ENABLED(THERMAL_PROTECTION_HOTENDS) && WATCH_TEMP_PERIOD > 0
+#if WATCH_HOTENDS
   /**
    * Start Heating Sanity Check for hotends that are below
    * their target temperature by a configurable margin.
   }
 #endif
 
-#if ENABLED(THERMAL_PROTECTION_BED) && WATCH_BED_TEMP_PERIOD > 0
+#if WATCH_THE_BED
   /**
    * Start Heating Sanity Check for hotends that are below
    * their target temperature by a configurable margin.

Marlin/temperature.h

       static volatile int babystepsTodo[3];
     #endif
 
-    #if ENABLED(THERMAL_PROTECTION_HOTENDS) && WATCH_TEMP_PERIOD > 0
+    #if WATCH_HOTENDS
       static int watch_target_temp[HOTENDS];
       static millis_t watch_heater_next_ms[HOTENDS];
     #endif
 
-    #if ENABLED(THERMAL_PROTECTION_BED) && WATCH_BED_TEMP_PERIOD > 0
+    #if WATCH_THE_BED
       static int watch_target_bed_temp;
       static millis_t watch_bed_next_ms;
     #endif
     }
     static float degTargetBed() { return target_temperature_bed; }
 
-    #if ENABLED(THERMAL_PROTECTION_HOTENDS) && WATCH_TEMP_PERIOD > 0
+    #if WATCH_HOTENDS
       static void start_watching_heater(uint8_t e = 0);
     #endif
 
-    #if ENABLED(THERMAL_PROTECTION_BED) && WATCH_BED_TEMP_PERIOD > 0
+    #if WATCH_THE_BED
       static void start_watching_bed();
     #endif
 
           start_preheat_time(HOTEND_INDEX);
       #endif
       target_temperature[HOTEND_INDEX] = celsius;
-      #if ENABLED(THERMAL_PROTECTION_HOTENDS) && WATCH_TEMP_PERIOD > 0
+      #if WATCH_HOTENDS
         start_watching_heater(HOTEND_INDEX);
       #endif
     }
 
     static void setTargetBed(const float& celsius) {
       target_temperature_bed = celsius;
-      #if ENABLED(THERMAL_PROTECTION_BED) && WATCH_BED_TEMP_PERIOD > 0
+      #if WATCH_THE_BED
         start_watching_bed();
       #endif
     }

Marlin/ultralcd.cpp

   /**
    * Watch temperature callbacks
    */
-  #if ENABLED(THERMAL_PROTECTION_HOTENDS) && WATCH_TEMP_PERIOD > 0
+  #if WATCH_HOTENDS
     #if TEMP_SENSOR_0 != 0
       void watch_temp_callback_E0() { thermalManager.start_watching_heater(0); }
     #endif
     #endif // HOTENDS > 3
   #endif
 
-  #if ENABLED(THERMAL_PROTECTION_BED) && WATCH_BED_TEMP_PERIOD > 0
-    #if TEMP_SENSOR_BED != 0
-      void watch_temp_callback_bed() { thermalManager.start_watching_bed(); }
-    #endif
-  #else
-    #if TEMP_SENSOR_BED != 0
-      void watch_temp_callback_bed() {}
-    #endif
+  #if WATCH_THE_BED
+    void watch_temp_callback_bed() { thermalManager.start_watching_bed(); }
   #endif
 
   #if ENABLED(FILAMENT_CHANGE_FEATURE)
     //
     // Bed:
     //
-    #if TEMP_SENSOR_BED != 0
+    #if WATCH_THE_BED
       MENU_MULTIPLIER_ITEM_EDIT_CALLBACK(int3, MSG_BED, &thermalManager.target_temperature_bed, 0, BED_MAXTEMP - 15, watch_temp_callback_bed);
     #endif
 
     //
     // Bed:
     //
-    #if TEMP_SENSOR_BED != 0
+    #if WATCH_THE_BED
       MENU_MULTIPLIER_ITEM_EDIT_CALLBACK(int3, MSG_BED, &thermalManager.target_temperature_bed, 0, BED_MAXTEMP - 15, watch_temp_callback_bed);
     #endif