Fix potential FPE in selection tests

Fix potential FPE in selection tests

Always initialize dynamic evaluation results to zero during the static
analysis pass.  The old code tried to do that, but missed a few cases
where the same expression was evaluated more than once.  Even during
static analysis, some dynamic arithmetic expressions are actually
evaluated, which could lead to FPE if the memory was uninitialized, even
though the results of the evaluation were never used.

Part of #1677.

Change-Id: I0cf73eb656d58f7ad08f6e12705c6d8a273adf84