display_status: stops M73 from setting progress to 0 if P missing

Signed-off-by: Pedro Lamas <pedrolamas@gmail.com>

docs/Config_Changes.md

@@ -8,6 +8,8 @@ All dates in this document are approximate.
 
 ## Changes
 
+20220307: `M73` will no longer set print progress to 0 if `P` is missing.
+
 20220304: There is no longer a default for the `extruder` parameter of
 [extruder_stepper](Config_Reference.md#extruder_stepper) config
 sections. If desired, specify `extruder: extruder` explicitly to

klippy/extras/display_status.py

@@ -30,10 +30,12 @@ class DisplayStatus:
                 progress = sdcard.get_status(eventtime)['progress']
         return { 'progress': progress, 'message': self.message }
     def cmd_M73(self, gcmd):
-        progress = gcmd.get_float('P', 0.) / 100.
-        self.progress = min(1., max(0., progress))
-        curtime = self.printer.get_reactor().monotonic()
-        self.expire_progress = curtime + M73_TIMEOUT
+        progress = gcmd.get_float('P', None)
+        if progress is not None:
+            progress = progress / 100.
+            self.progress = min(1., max(0., progress))
+            curtime = self.printer.get_reactor().monotonic()
+            self.expire_progress = curtime + M73_TIMEOUT
     def cmd_M117(self, gcmd):
         msg = gcmd.get_raw_command_parameters() or None
         self.message = msg