Revert "no need to load the buffer, we already have it"

This reverts commit 8ea3620.

Fixes #485 #486 #487

python3/vdebug/ui/vimui.py

@@ -598,6 +598,7 @@ def destroy(self, wipeout=True):
         if self._buffer is None:
             return
         self.is_open = False
+        self._buffer = HiddenBuffer(self._buffer.contents())
         if wipeout and int(vim.eval('buffer_exists("%s")' % self.name)) == 1:
             vim.command('bwipeout %s' % self.name)
         self.on_destroy()