Improvement: All off switches only active channels off

devices/__init__.py

         if self.flash_active:
             self.all_off_requested = True
         else:
-            self.set_output_0(False)
-            self.set_output_1(False)
+            if self.output_0:
+                self.set_output_0(False)
+            if self.output_1:
+                self.set_output_1(False)
 
 
 class silvercrest_powerplug(base):
         self.set_output_0('toggle')
 
     def all_off(self):
-        self.set_output_0(False)
+        if self.output_0:
+            self.set_output_0(False)
 
 
 class silvercrest_motion_sensor(base):
         self.set_color_temp(data)
 
     def all_off(self):
-        self.set_output_0(False)
+        if self.output_0:
+            self.set_output_0(False)
 
 
 class tradfri_button(base):