poll: Add missing padding for options placeholder text

Previously, the 5px bottom padding only existed when there were option
rows. This padding should be applied to the placeholder text as well.

Signed-off-by: Zixuan James Li <[email protected]>

Author: PIG208

lib/widgets/poll.dart

@@ -113,8 +113,11 @@ class _PollWidgetState extends State<PollWidget> {
       children: [
         Padding(padding: const EdgeInsets.only(bottom: 6), child: question),
         if (widget.poll.options.isEmpty)
-          Text(zulipLocalizations.pollWidgetOptionsMissing,
-            style: textStyleVoterNames.copyWith(fontStyle: FontStyle.italic)),
+          Padding(
+            // This is consistent with the option rows' bottom padding.
+            padding: const EdgeInsets.only(bottom: 5),
+            child: Text(zulipLocalizations.pollWidgetOptionsMissing,
+              style: textStyleVoterNames.copyWith(fontStyle: FontStyle.italic))),
         for (final option in widget.poll.options)
           buildOptionItem(option),
       ]);