Fix atom value parsing in SETPROP

xprop(1) encloses the returned atom string value in double quotes while
it doesn't when the value is unset. Original simple parsing would fail
and parse the atom name instead of getting an empty value.

Signed-off-by: Christoph Lohmann <20h@r-36.net>

config.def.h

@@ -37,7 +37,9 @@ static Bool allowgeolocation      = TRUE;
 
 #define SETPROP(p, q) { \
 	.v = (char *[]){ "/bin/sh", "-c", \
-		"prop=\"`xprop -id $2 $0 | cut -d '\"' -f 2 | xargs -0 printf %b | dmenu`\" &&" \
+		"prop=\"`xprop -id $2 $0 " \
+		"| sed \"s/^$0(STRING) = \\(\\\\\"\\?\\)\\(.*\\)\\1$/\\2/\" " \
+		"| xargs -0 printf %b | dmenu`\" &&" \
 		"xprop -id $2 -f $1 8s -set $1 \"$prop\"", \
 		p, q, winid, NULL \
 	} \