Fix buffer overrun in I_ClipboardPaste

src/sdl/i_system.c

@@ -2726,10 +2726,10 @@ const char *I_ClipboardPaste(void)
 
 	if (!SDL_HasClipboardText())
 		return NULL;
+
 	clipboard_contents = SDL_GetClipboardText();
-	memcpy(clipboard_modified, clipboard_contents, 255);
+	strlcpy(clipboard_modified, clipboard_contents, 256);
 	SDL_free(clipboard_contents);
-	clipboard_modified[255] = 0;
 
 	while (*i)
 	{