tracker issue : CF-4207294

Problem Description: Referencing an undefined struct value in a <cfif> statement causes a crash in unreachable code in some cases.  Using, for example, `<cfif someFunction({key: object.value})>` causes a crash when `object.value` is undefined, even if that code is not reachable.  In the reproduction case below the crash only occurs in a nested if statement.  The outer if statement must have a corresponding else.

Steps to Reproduce:
Use the following fiddle: https://cffiddle.org/app/file?filepath=8df88b36-6681-4a28-a8e9-6df7178c1f4b/62cd2478-e562-4694-9c3e-c3a04429d13d/8c6bbcb1-3fa9-47a4-97ff-9124252f6046.cfm

The code is copied below for convenience.
```
<cfset jsonObj = '{"foo":"bar","monthID": null}'>
<cfset obj = DeserializeJSON(jsonObj)>

<cfif false>
  <!--- This is impossible to reach, but there's a crash on line 6. --->
  <cfif check({
    "monthID": obj.monthID
  })>
  </cfif>
<cfelse> <!--- Remove cfelse and the error does not occur. --->
</cfif>
```

The code appears to crash on CF 2018 as well.

Actual Result:
Crash on line 6, even though line 6 is unreachable and not executed.  (In our actual code we have validation around the undefined value in question, but that code does not run.)

Expected Result:
The code should not crash.  It's not even executed.
Any Workarounds:
Remove the cfelse.
Use a variable to hold `check`'s argument (e.g. don't supply an anonymous struct).
Don't use a nest <cfif>
Use <cfset> instead of <cfif> and a intermediary variable to hold the return value.

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