Delete sms from draft box

Delete sms from draft box

I found some topic but they were not helped me to solve my problem. I want
to delete my draft sms. Have tried with this uri so many time:
contentResolver.delete("content://sms/draft", " ", null); //this is line
173
It throws this exeption:
09-09 00:43:43.454: E/AndroidRuntime(2933): Caused by:
java.lang.IllegalArgumentException: Unknown URL
09-09 00:43:43.454: E/AndroidRuntime(2933): at
android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java)
09-09 00:43:43.454: E/AndroidRuntime(2933): at
android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java)
09-09 00:43:43.454: E/AndroidRuntime(2933): at
android.content.ContentProviderProxy.delete(ContentProviderNative.java)
09-09 00:43:43.454: E/AndroidRuntime(2933): at
android.content.ContentResolver.delete(ContentResolver.java)
09-09 00:43:43.454: E/AndroidRuntime(2933): at
com.haanz.smsbackup.SmsProvider.query(SmsProvider.java:173)
09-09 00:43:43.454: E/AndroidRuntime(2933): at
android.content.ContentProvider.query(ContentProvider.java)
09-09 00:43:43.454: E/AndroidRuntime(2933): at
android.content.ContentProvider$Transport.query(ContentProvider.java)
09-09 00:43:43.454: E/AndroidRuntime(2933): at
android.content.ContentResolver.query(ContentResolver.java)
09-09 00:43:43.454: E/AndroidRuntime(2933): at
android.content.ContentResolver.query(ContentResolver.java)
Anybody please tell me where did I wrong?