Turn NULL used as int to 0.

app/clipboard/clipboard_linux.cc

Index: app/clipboard/clipboard_linux.cc
diff --git a/app/clipboard/clipboard_linux.cc b/app/clipboard/clipboard_linux.cc
index 8b30ffda3ebfd46cfaa64d7000cfc1101dad6dcf..bc8a0b4db26283e30cd8f46e7f964624010e0bf9 100644
--- a/app/clipboard/clipboard_linux.cc
+++ b/app/clipboard/clipboard_linux.cc
@@ -204,7 +204,7 @@ void Clipboard::WriteBookmark(const char* title_data, size_t title_len,
   // Write as a URI.
   char* data = new char[url_len + 1];
   memcpy(data, url_data, url_len);
-  data[url_len] = NULL;
+  data[url_len] = '\0';
   InsertMapping(kMimeURI, data, url_len + 1);
 }