ranap_parse_lai(): properly initialize out-arg, adjust test experr

The test stderr output changes merely because the source code line numbers
of the error logging changed.

Fixes: CID#93770
diff --git a/src/tests/test-helpers.err b/src/tests/test-helpers.err
index 9c04723..81b79e1 100644
--- a/src/tests/test-helpers.err
+++ b/src/tests/test-helpers.err
@@ -1,3 +1,3 @@
-<0004> ranap_common.c:504 Invalid PLMN Identity size: should be 3, is 2
-<0004> ranap_common.c:518 Invalid LAC size: should be 2, is 1
+<0004> ranap_common.c:508 Invalid PLMN Identity size: should be 3, is 2
+<0004> ranap_common.c:522 Invalid LAC size: should be 2, is 1
 
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