Trac #33213: don't reset expect interfaces when starting them.

src/sage/interfaces/expect.py

@@ -440,7 +440,12 @@ def _do_cleaner(self):
 
     def _start(self, alt_message=None, block_during_init=True):
         from sage.misc.misc import sage_makedirs
-        self.quit()  # in case one is already running
+
+        if self.is_running():
+            # In case one is already running. We check first because
+            # quit() can reset the local temporary filename at an
+            # unexpected time as the process is started "on demand."
+            self.quit()
 
         self._session_number += 1