make ?stack work anywhere

copyparty/httpcli.py

@@ -1474,7 +1474,7 @@ class HttpCli(object):
         raise Pebkac(500, x)
 
     def tx_stack(self):
-        if not self.readable or not self.writable:
+        if not self.avol:
             raise Pebkac(403, "not admin")
 
         if self.args.no_stack:

copyparty/web/splash.html

@@ -35,7 +35,7 @@
             </table>
         </td></tr></table>
         <div class="btns">
-            <a href="{{ avol[0] }}?stack">dump stack</a>
+            <a href="/?stack">dump stack</a>
         </div>
         {%- endif %}