If you want to change occurrences of "the empty string" to "the empty String", here they are:
6.1.7 / para 2
18.2.4 / step 3
18.2.5 / step 3
19.2.3.2 / step 14
19.4.3.2.1 / step 3
21.1.2.1 / step 6
21.1.2.2 / step 6
21.1.2.4 / step 9
21.1.2.4 / step 12.e.i
B.2.1.1 / step 4
Also, there are a few occurrences of 'the string "..."':
7.1.6 / para 1
15.2.1.16.3 / note / para 2
24.3.2.3. / step 8.c.ii