Bugfix: Don’t focus the wrong workspace when moving to scratchpad (+test) (Thanks loblik)

The problem was that scratchpad_move() didn’t check whether the source
workspace was focused. Therefore, 'move scratchpad' only worked reliably
interactively , but not when used with criteria.

testcases/t/198-regression-scratchpad-crash.t

@@ -0,0 +1,19 @@
+#!perl
+# vim:ts=4:sw=4:expandtab
+# When using a command which moves a window to scratchpad from an invisible
+# (e.g. unfocused) workspace and immediately shows that window again, i3
+# crashed.
+# Bug still in: 4.2-305-g22922a9
+use i3test;
+
+my $ws1 = fresh_workspace;
+my $invisible_window = open_window;
+my $other_focusable_window = open_window;
+
+my $ws2 = fresh_workspace;
+my $id = $invisible_window->id;
+cmd qq|[id="$id"] move scratchpad, scratchpad show|;
+
+does_i3_live;
+
+done_testing;