MainWindow: Try fix backup saved for multi scenario.

src/Model/Study.py

@@ -126,15 +126,12 @@ class Study(SQLModel):
 
         is_new = False
         fname = fname + "." + str(self._old_save_id)
-        if os.path.exists(self.filename) and ".backup" not in self.filename:
+        if os.path.exists(self.filename):
             filename = os.path.join(fdir, "_PAMHYR_", "__old__", fname)
             logger.debug(f"Backup previous version copy: {filename}")
             shutil.copy(self.filename, filename)
             self._old_save_id += 1
 
-        if ".backup" in self.filename:
-            is_new = True
-
         if not os.path.exists(self.filename):
             is_new = True