Could not read row 0, column 0 from CursorWindow which has 0 rows, 1 column

I have an Android app that is trying to download a blob from a SQLite database as a byte array:

public byte[] getBytesForId(long id){
    byte[] result = null;
    String sql =  "SELECT _blob FROM test_table WHERE _id=?";
    String[] selection = new String[] { String.valueOf(id) };

    Cursor mCursor = super.DB().rawQuery(sql, selection);

    if ( mCursor != null && mCursor.moveToFirst() ) {               
        if (mCursor.getCount() > 0)
            result = mCursor.getBlob(0);

        if (mCursor != null && !mCursor.isClosed())
            mCursor.close();
    }

    return result;
}

      

        
        
        
      

    

but I am getting the following exception:

Failed to read row 0, column 0 from a CursorWindow which has 0 rows, 1 columns.
java.lang.IllegalStateException: Couldn't read row 0, col 0 from CursorWindow.  Make sure the Cursor is initialized correctly before accessing data from it.
at android.database.CursorWindow.nativeGetBlob(Native Method)
at android.database.CursorWindow.getBlob(CursorWindow.java:404)
at android.database.AbstractWindowedCursor.getBlob(AbstractWindowedCursor.java:45)
at com.test.testapp.model.DbClass.getBytesForId(DbClass.java:218)
at com.test.testapp.TestService.StepThroughBlocks(TestService.java:434)
at com.test.testapp.TestService.checkBlocks(TestService.java:378)
at com.test.testapp.TestService.access$4(TestService.java:357)
at com.test.testapp.TestService$2.run(TestService.java:315)
at java.lang.Thread.run(Thread.java:841)

      

        
        
        
      

    

Of course, if I check that the cursor has some data first ...

if ( mCursor != null && mCursor.moveToFirst() ) 
        if (mCursor.getCount() > 0)
            result = mCursor.getBlob(0);

      

        
        
        
      

    

... I shouldn't get this exception? I added the line mCursor.getCount which might help, but I still get the exception. How is this possible?