Fix overflow spotted by jmb/valgrind.

svn path=/trunk/netsurf/; revision=4800

gtk/gtk_throbber.c

@@ -50,7 +50,7 @@ bool nsgtk_throbber_initialise_from_png(const int frames, ...)
 		return false;
 	}
 	
-	throb = malloc(sizeof(throb));
+	throb = malloc(sizeof(*throb));
 	throb->nframes = frames;
 	throb->framedata = malloc(sizeof(GdkPixbuf *) * throb->nframes);