fixup! psa: Disallow use of invalid cipher contexts

Author: Patater

tests/suites/test_suite_psa_crypto.function

@@ -2525,8 +2525,8 @@ exit:
 /* BEGIN_CASE */
 void cipher_operation_init( )
 {
-    const uint8_t input[1];
-    unsigned char output[1];
+    const uint8_t input[1] = { 0 };
+    unsigned char output[1] = { 0 };
     size_t output_length;
     /* Test each valid way of initializing the object, except for `= {0}`, as
      * Clang 5 complains when `-Wmissing-field-initializers` is used, even