Revert "manage: For isfloating/oldstate check/set, ensure trans client actually exists"

This reverts commit bece862a.

It caused a regression, for example:
https://lists.suckless.org/hackers/2203/18220.html

dwm.c

@@ -1065,7 +1065,7 @@ manage(Window w, XWindowAttributes *wa)
 	XSelectInput(dpy, w, EnterWindowMask|FocusChangeMask|PropertyChangeMask|StructureNotifyMask);
 	grabbuttons(c, 0);
 	if (!c->isfloating)
-		c->isfloating = c->oldstate = t || c->isfixed;
+		c->isfloating = c->oldstate = trans != None || c->isfixed;
 	if (c->isfloating)
 		XRaiseWindow(dpy, c->win);
 	attach(c);