Given the placement.txt with the content:
```
9:exclude(placement(10))
10:country("DE")
```
Without patch:
```
placement-test --placement=/tmp/placement.txt countrycode=DE
Error: type mismatch: reflect: Call using zero Value argument
```
With the patch:
```
placement-test --placement=/tmp/placement.txt countrycode=DE
Error: Error in line 'exclude(placement(10))' when placement rule is parsed: Placement 10 is referenced before defined. Please define it first!
```
Change-Id: I9ad81016d4a57fdb32f3ff9031b5591f9a7cd2a6
c3fbac2e7a