Bugfix: don't try to resize docks by command

cmd_resize does not implement a method to resize dock clients.

A command like `[instance=".*"] resize grow width 160 px or 16 ppt`
when a dock client matched would crash i3.

fixes #1201

src/commands.c

@@ -779,6 +779,12 @@ void cmd_resize(I3_CMD, char *way, char *direction, char *resize_px, char *resiz
 
     owindow *current;
     TAILQ_FOREACH(current, &owindows, owindows) {
+        /* Don't handle dock windows (issue #1201) */
+        if (current->con->window->dock) {
+            DLOG("This is a dock window. Not resizing (con = %p)\n)", current->con);
+            continue;
+        }
+
         Con *floating_con;
         if ((floating_con = con_inside_floating(current->con))) {
             cmd_resize_floating(current_match, cmd_output, way, direction, floating_con, px);

testcases/t/222-regress-dock-resize.t

@@ -0,0 +1,42 @@
+#!perl
+# vim:ts=4:sw=4:expandtab
+#
+# Please read the following documents before working on tests:
+# • http://build.i3wm.org/docs/testsuite.html
+#   (or docs/testsuite)
+#
+# • http://build.i3wm.org/docs/lib-i3test.html
+#   (alternatively: perldoc ./testcases/lib/i3test.pm)
+#
+# • http://build.i3wm.org/docs/ipc.html
+#   (or docs/ipc)
+#
+# • http://onyxneon.com/books/modern_perl/modern_perl_a4.pdf
+#   (unless you are already familiar with Perl)
+#
+# Test that i3 does not crash when a command is issued that would resize a dock
+# client.
+# Ticket: #1201
+# Bug still in: 4.7.2-107-g9b03be6
+use i3test i3_autostart => 0;
+
+my $config = <<'EOT';
+# i3 config file (v4)
+font -misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1
+EOT
+
+my $pid = launch_with_config($config);
+
+my $i3 = i3(get_socket_path());
+$i3->connect()->recv;
+
+my $window = open_window(
+    wm_class => 'special',
+    window_type => $x->atom(name => '_NET_WM_WINDOW_TYPE_DOCK'),
+);
+
+cmd('[class="special"] resize grow height 160 px or 16 ppt');
+
+does_i3_live;
+
+done_testing;