Merge upstream dev companion CLI updates

src/helpers/ConfigSerializer.cpp

@@ -90,6 +90,12 @@ int ConfigSerializer::Context::readNext() {
     case EXPECT_COMMA_OR_KEY:
       if (c == ',') { rd_mode = EXPECT_KEY; return TOK_WHITESPACE; }
     case EXPECT_KEY:
+      // Empty objects are valid and are emitted by serializers such as the
+      // dynamic `custom` preferences object before it has any entries.
+      if (rd_len == 0 && c == '}') {
+        rd_mode = EXPECT_COMMA_OR_KEY_OR_CLOSE;
+        return TOK_END_OBJ;
+      }
       if (rd_len > 0 && c == ':') { rd_buf[rd_len] = 0; rd_len = 0; rd_mode = EXPECT_VAL_OR_OBJ; return TOK_KEY; }
       if (rd_len == 0 && is_whitespace(c)) return TOK_WHITESPACE;
       if (rd_len < CONFIG_MAX_KEYLEN-1 && is_key_char(c)) { rd_buf[rd_len++] = c; return TOK_WHITESPACE; }