Fixed bug on incorrectly revisiting same block.

Rationale:
Aart's fuzz tester found this particular bug, where
revisiting a block (after dynamic bce) would cause
static array length based bce to feed into itself
and thus incorrectly remove a needed bounds check.

bug=27376274

Change-Id: I9163f283af355d444b4cec707f194fe2b67c2572