clients: use xmalloc in more places

For the clients continue to use xmalloc() to simplify OOM-handling.

Signed-off-by: Brian Lovin <brian.j.lovin@intel.com>
diff --git a/clients/dnd.c b/clients/dnd.c
index 140f3f4..ff46fd7 100644
--- a/clients/dnd.c
+++ b/clients/dnd.c
@@ -391,7 +391,7 @@
 	y -= allocation.y;
 
 	if (item && state == WL_POINTER_BUTTON_STATE_PRESSED) {
-		dnd_drag = malloc(sizeof *dnd_drag);
+		dnd_drag = xmalloc(sizeof *dnd_drag);
 		dnd_drag->dnd = dnd;
 		dnd_drag->input = input;
 		dnd_drag->time = time;
@@ -567,9 +567,7 @@
 	int32_t width, height;
 	unsigned int i;
 
-	dnd = malloc(sizeof *dnd);
-	if (dnd == NULL)
-		return dnd;
+	dnd = xmalloc(sizeof *dnd);
 	memset(dnd, 0, sizeof *dnd);
 
 	dnd->window = window_create(display);