fix(jid): treat NULL/empty/"(null)" barejid the same as resource

src/database_flatfile_parser.c

@@ -465,7 +465,8 @@ ff_write_line(FILE* fp, const char* timestamp, const char* type, const char* enc
     if (safe_rid) {
         g_string_append_printf(meta, "|corrects:%s", safe_rid);
     }
-    if (to_jid && strlen(to_jid) > 0) {
+    if (to_jid && strlen(to_jid) > 0
+        && g_strcmp0(to_jid, "(null)") != 0) {
         auto_gchar gchar* safe_to = ff_escape_meta_value(to_jid);
         g_string_append_printf(meta, "|to:%s", safe_to);
     }
@@ -481,7 +482,9 @@ ff_write_line(FILE* fp, const char* timestamp, const char* type, const char* enc
 
     // Build sender — escape ": " in the resource part to prevent
     // the parser from splitting at the wrong point.
-    GString* sender = g_string_new(from_jid ? from_jid : "unknown");
+    const gboolean from_jid_usable = from_jid && *from_jid
+                                     && g_strcmp0(from_jid, "(null)") != 0;
+    GString* sender = g_string_new(from_jid_usable ? from_jid : "unknown");
     if (from_resource && strlen(from_resource) > 0
         && g_strcmp0(from_resource, "(null)") != 0) {
         // Escape backslash and colon-space in resource

src/xmpp/jid.c

@@ -113,7 +113,12 @@ jid_create_from_bare_and_resource(const char* const barejid, const char* const r
 {
     // NULL, empty, or the literal "(null)" (legacy artefact from earlier
     // builds where g_strdup_printf("%s", NULL) leaked the glibc placeholder
-    // into stored resourceparts) all mean "no resource" — return a bare jid.
+    // into stored data) all mean "no value" for either part. With no usable
+    // bare jid there is nothing to construct; with no usable resource we
+    // return the bare jid alone.
+    if (!barejid || !*barejid || g_strcmp0(barejid, "(null)") == 0) {
+        return NULL;
+    }
     if (!resource || !*resource || g_strcmp0(resource, "(null)") == 0) {
         return jid_create(barejid);
     }