Preprocessor: do not crash when unknown symbol is passed to “irf_shocks” option

Ref. preprocessor#57

Preprocessor: do not crash when unknown symbol is passed to “irf_shocks” option
24b0fed6 · Sébastien Villemot · ff562144 · 033e6efa · bd64c91c · 033e6efa
Verified Commit 24b0fed6 authored 4 years ago by Sébastien Villemot
--- a/preprocessor @ 033e6efa
+++ b/preprocessor @ 033e6efa
-Subproject commit bd64c91ca47bf840deb83bd51332467b7c97dd54
+Subproject commit 033e6efa28d141a97fec2e2c2365b99a9b722c9c