compiler: do not crash on fallback ffi with `extern` without a string

Signed-off-by: Jean Privat <jean@pryen.org>

diff --git a/src/compiler/abstract_compiler.nit b/src/compiler/abstract_compiler.nit
index eea089a..0943964 100644 (file)
--- a/src/compiler/abstract_compiler.nit
+++ b/src/compiler/abstract_compiler.nit
@@ -2151,7 +2151,7 @@ redef class AMethPropdef
        do
                var externname
                var at = self.get_single_annotation("extern", v.compiler.modelbuilder)
-               if at != null then
+               if at != null and at.n_args.length == 1 then
                        externname = at.arg_as_string(v.compiler.modelbuilder)
                        if externname == null then return false
                else