p4 says:

If the expression P points to element x[i] of an array object x with n elements, the expressions P + J and J + P (where J has the value j) point to the (possibly-hypothetical) element x[i + j] if 0 ≤ i + j ≤ n; otherwise, the behavior is undefined.

Semicolon suggests that "otherwise" applies to the first clause of the compound sentence, to both preconditions: expression shall point to an element of an array object and the inequalities shall be satisfied. Therefore, if the first precondition is not met, the behavior is undefined.

But p7 allows adding the value 0 to a null pointer value, which, of course, does not point to an element of any array object.