Only print marked files when -o is given

Fallback to print all files, if no images are marked, was kind of
irritating.

Makefile

@@ -1,4 +1,4 @@
-VERSION = git-20130810
+VERSION = git-20130822
 
 PREFIX    = /usr/local
 MANPREFIX = $(PREFIX)/share/man

README.md

@@ -79,7 +79,7 @@ of small previews is displayed, making it easy to choose an image to open.
     -i           Read file list from stdin
     -n NUM       Start at picture NUM
     -N NAME      Set X window resource name to NAME
-    -o           Write list of marked/all files to stdout when quitting
+    -o           Write list of marked files to stdout when quitting
     -p           Pixelize, i.e. turn off image anti-aliasing
     -q           Be quiet, disable warnings
     -r           Search given directories recursively for images

commands.c

@@ -61,9 +61,9 @@ bool it_quit(arg_t a)
 {
 	unsigned int i;
 
-	if (options->to_stdout) {
+	if (options->to_stdout && markcnt > 0) {
 		for (i = 0; i < filecnt; i++) {
-			if (!markcnt || files[i].marked)
+			if (files[i].marked)
 				printf("%s\n", files[i].name);
 		}
 	}

sxiv.1

@@ -62,10 +62,10 @@ Print brief usage information to standard output and exit.
 Read names of files to open from standard input.
 .TP
 .B \-o
-Write list of all marked files, or all opened files if no files are marked, to
-standard output when quitting. If combined with
-.IR \-i ,
-then sxiv acts as a visual filter/pipe.
+Write list of all marked files to standard output when quitting. In combination
+with
+.I \-i
+sxiv can be used as a visual filter/pipe.
 .TP
 .B \-p
 Pixelize images, i.e. turn off anti-aliasing.