Fix ‘-e’ switch when ‘%E’ escape in ‘tab-arguments’ option is present

Perl interprets ‘$#$root->{argv}’ as ‘($#$root)->{argv}’ which causes
and error since ‘$root’ is not an array reference:

    urxvt: Not an ARRAY reference at /home/wd/.urxvt/ext/tabbedex line 806.

This would trigger whenever ‘-e’ switch and ‘%E’ escape in
‘tab-arguments’ option were used together.  Fix by adding braces to
change binding of the operators.

Fixes: #33

tabbedex

@@ -801,7 +801,7 @@ sub args_percent_substitution {
 		quote_words @{ $root->{argv} }
 	} elsif ($ch eq 'E') {
 		quote_words @{ $root->{argv} }
-			? @{ $root->{argv} }[1..$#$root->{argv}]
+			? @{ $root->{argv} }[1..$#{ $root->{argv} }]
 			: ($ENV{SHELL} || '/bin/sh')
 	} elsif ($ch eq 'p') {
 		$tab ? $tab->foreground_pgid : -1