Better remove empty blocks. Now works for practically empty tracks. Cosmetic bug still present when removing content linked blocks and then do undo

engine/api.py

@@ -772,6 +772,7 @@ def deleteCurrentBlock():
 def deleteEmptyBlocks():
     """whole score"""
     dictOfTrackIdsWithListOfBlockIds = session.data.removeEmptyBlocks()
+    #We keep everything in dictOfTrackIdsWithListOfBlockIds. Empty blocks have been removed from this data.
     if dictOfTrackIdsWithListOfBlockIds and all(l for l in dictOfTrackIdsWithListOfBlockIds.values()):
         rearrangeBlocksInMultipleTracks(dictOfTrackIdsWithListOfBlockIds)  #handles undo and callbacks for redrawing
     callbacks._setCursor()

engine/main.py

@@ -1023,11 +1023,18 @@ class Data(template.engine.sequencer.Score):
         
         #for trId, track in Track.allTracks.items():
         for track in list(self.hiddenTracks.keys()) + self.tracks:
+            if len(track.blocks) <= 1:
+                continue #next track
+                
+            #Get all blocks and then remove those with no content.
             trId = id(track)
-            listOfBlockIds = track.asListOfBlockIds()
+            listOfBlockIds = track.asListOfBlockIds()            
             for block in track.blocks:
-                if not block.data and len(track.blocks) > 1:
+                if not block.data:                    
                     listOfBlockIds.remove(id(block))
+            #Maybe the track was empty. In this case we add one of the blocks again. Otherwise follow up functions will not act.
+            if not listOfBlockIds:
+                listOfBlockIds.append(id(block))
             dictOfTrackIdsWithListOfBlockIds[trId] = listOfBlockIds
         return dictOfTrackIdsWithListOfBlockIds