Fixed race when closing an auto-saving project.

Turning off the timer for saveTimerNoChanges just like the code
already did in closeProject() for saveTimer fixes this bug. Easy.

But how to prevent this kind of race condition in the future?

Several related routines have been adjusted to fail gracefully or report
a bug to the console when something goes wrong, depending on what is
most suitable for that bit of logic.

manuskript/load_save/version_1.py

@@ -118,7 +118,14 @@ def saveProject(zip=None):
     # List of files to be moved
     moves = []
 
+    # MainWindow interaction things.
     mw = mainWindow()
+    project = mw.currentProject
+
+    # Sanity check (see PR-583): make sure we actually have a current project.
+    if project is None:
+        print("Error: cannot save project because there is no current project in the UI.")
+        return False
 
     # File format version
     files.append(("MANUSKRIPT", "1"))
@@ -295,10 +302,8 @@ def saveProject(zip=None):
 
     files.append(("settings.txt", settings.save(protocol=0)))
 
-    project = mw.currentProject
-
     # We check if the file exist and we have write access. If the file does
-    # not exists, we check the parent folder, because it might be a new project.
+    # not exist, we check the parent folder, because it might be a new project.
     if os.path.exists(project) and not os.access(project, os.W_OK) or \
        not os.path.exists(project) and not os.access(os.path.dirname(project), os.W_OK):
         print("Error: you don't have write access to save this project there.")

manuskript/mainWindow.py

@@ -695,6 +695,7 @@ class MainWindow(QMainWindow, Ui_MainWindow):
         # Clear datas
         self.loadEmptyDatas()
         self.saveTimer.stop()
+        self.saveTimerNoChanges.stop()
         loadSave.clearSaveCache()
 
         self.breakConnections()
@@ -818,6 +819,13 @@ class MainWindow(QMainWindow, Ui_MainWindow):
         # risk a scenario where the timer somehow triggers a new save while saving.
         self.saveTimerNoChanges.stop()
 
+        if self.currentProject is None:
+            # No UI feedback here as this code path indicates a race condition that happens
+            # after the user has already closed the project through some way. But in that
+            # scenario, this code should not be reachable to begin with.
+            print("Bug: there is no current project to save.")
+            return
+
         r = loadSave.saveProject()  # version=0
 
         projectName = os.path.basename(self.currentProject)