Tapset aliases may speculatively manipulate $variables or @cast expressions
that may be expected to fail sometimes.  In some cases, the tapset author
may remember to wrap these e.g. in try / catch blocks.  As an enhancement
to the existing --skip-badvars option that's narrowly focused on $var
runtime errors, we could introduce an implicit try / catch over alias
prologues:

probe a = foo { ..handler prologue.. }
probe a { ..handler.. }

to expand to:

    try {
     ..handler prologue..
    } catch { next }
    ..handler..

It may make sense to credit such events against the MAXSKIPPED counter.