Check empty file cancellation and keep test capture semantics aligned

tools/chatgui/tests/test_member_files_browser.cpp

@@ -71,6 +71,7 @@ extern "C" int gui_bridge_member_files_transfer(const mf_transfer_request* reque
     return 0;
 }
 extern "C" int gui_bridge_member_files_cancel(uint64_t id) {
+    if (!id) return 0;
     if (!ready) return -1;
     cancelled.append(id); return 0;
 }

tools/chatgui/tests/test_member_files_lifecycle.cpp

@@ -215,7 +215,7 @@ private slots:
             QCOMPARE(u_get_allocated_count(), baseline);
             QCOMPARE(gui_bridge_member_files_cancel(100), 0); gui_bridge_set_inst(nullptr);
             QCOMPARE(u_get_allocated_count(), baseline); QVERIFY(gui_bridge_member_files_cancel(101) < 0);
-            core.attach(); QVERIFY(gui_bridge_member_files_cancel(0) < 0);
+            core.attach(); QCOMPARE(gui_bridge_member_files_cancel(0), 0);
 #ifdef UTUN_TEST_FILE_ALLOC_FAILURES
             for (int point : {1, 2}) {
                 failAllocation = point; QVERIFY(gui_bridge_member_files_cancel(102) < 0); QCOMPARE(failAllocation, 0);