code-style: simplify some checks

main change here is making the `zoom()` logic saner. the rest of the
changes are just small stuff which accumulated on my local branch.

pop() must not be called with NULL. and `zoom()` achieves this, but in a
very (unnecessarily) complicated way:

if c == NULL then nexttiled() will return NULL as well, so we enter this
branch:

	if (c == nexttiled(selmon->clients))

in here the !c check fails and the function returns before calling pop()

		if (!c || !(c = nexttiled(c->next)))
			return;

however, none of this was needed. we can simply return early if c was NULL.
Also `c` is set to `selmon->sel` so we can use `c` in the first check
instead which makes things shorter.

dwm.c

@@ -918,13 +918,11 @@ gettextprop(Window w, Atom atom, char *text, unsigned int size)
 	text[0] = '\0';
 	if (!XGetTextProperty(dpy, w, &name, atom) || !name.nitems)
 		return 0;
-	if (name.encoding == XA_STRING)
+	if (name.encoding == XA_STRING) {
 		strncpy(text, (char *)name.value, size - 1);
-	else {
-		if (XmbTextPropertyToTextList(dpy, &name, &list, &n) >= Success && n > 0 && *list) {
-			strncpy(text, *list, size - 1);
-			XFreeStringList(list);
-		}
+	} else if (XmbTextPropertyToTextList(dpy, &name, &list, &n) >= Success && n > 0 && *list) {
+		strncpy(text, *list, size - 1);
+		XFreeStringList(list);
 	}
 	text[size - 1] = '\0';
 	XFree(name.value);
@@ -1099,9 +1097,7 @@ maprequest(XEvent *e)
 	static XWindowAttributes wa;
 	XMapRequestEvent *ev = &e->xmaprequest;
 
-	if (!XGetWindowAttributes(dpy, ev->window, &wa))
-		return;
-	if (wa.override_redirect)
+	if (!XGetWindowAttributes(dpy, ev->window, &wa) || wa.override_redirect)
 		return;
 	if (!wintoclient(ev->window))
 		manage(ev->window, &wa);
@@ -1603,7 +1599,6 @@ setup(void)
 	focus(NULL);
 }
 
-
 void
 seturgent(Client *c, int urg)
 {
@@ -2124,12 +2119,10 @@ zoom(const Arg *arg)
 {
 	Client *c = selmon->sel;
 
-	if (!selmon->lt[selmon->sellt]->arrange
-	|| (selmon->sel && selmon->sel->isfloating))
+	if (!selmon->lt[selmon->sellt]->arrange || !c || c->isfloating)
+		return;
+	if (c == nexttiled(selmon->clients) && !(c = nexttiled(c->next)))
 		return;
-	if (c == nexttiled(selmon->clients))
-		if (!c || !(c = nexttiled(c->next)))
-			return;
 	pop(c);
 }