[lldb] Fixed an invalid error message in the DAP disconnect response (#92345)

The `disconnect` response contains the `error` message with invalid
characters (a junk data). To reproduce this issue it is enough to run
the `TestDAP_commands` test on Windows host and Linux target. The test
will fail to run ELF file on Windows and dap_server will be disconnected
unexpectedly.

Note dap_server hangs if read_packet() cannot decode JSON with invalid
characters. read_packet() must return None in this case instead of an
exception. But dap_server does not require any fix after this patch.

Author: slydiman

lldb/tools/lldb-dap/lldb-dap.cpp

@@ -977,7 +977,7 @@ void request_disconnect(const llvm::json::Object &request) {
     g_dap.debugger.SetAsync(false);
     lldb::SBError error = terminateDebuggee ? process.Kill() : process.Detach();
     if (!error.Success())
-      response.try_emplace("error", error.GetCString());
+      EmplaceSafeString(response, "error", error.GetCString());
     g_dap.debugger.SetAsync(true);
     break;
   }