Memory leak in _webui_get_file_name_from_url

[studokim]

WebUI v2.4.2:

=================================================================
==461941==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 32 byte(s) in 3 object(s) allocated from:
    #0 0x6010a3b9f1ca in strdup llvmSrc/compiler-rt/lib/asan/asan_interceptors.cpp:570:3
    #1 0x6010a3de384c in _webui_get_file_name_from_url /src/webui.c:3009:18 _webui_get_file_name_from_url strdup
    #2 0x6010a3de38e8 in _webui_get_full_path_from_url src/webui.c:3032:18 _webui_get_full_path_from_url
    #3 0x6010a3de34b6 in _webui_serve_file src/webui.c:3116:27
    #4 0x6010a3de2314 in _webui_http_handler src/webui.c:6553:36
    #5 0x6010a3e1a61c in handle_request src/civetweb/civetweb.c:15224:8
    #6 0x6010a3e17134 in handle_request_stat_log src/civetweb/civetweb.c:6659:2
    #7 0x6010a3e14b0f in process_new_connection src/civetweb/civetweb.c:19705:5
    #8 0x6010a3e1334b in worker_thread_run src/civetweb/civetweb.c:20128:4
    #9 0x6010a3e126ec in worker_thread src/civetweb/civetweb.c:20189:2
    #10 0x6010a3bb3608 in asan_thread_start(void*) llvmSrc/compiler-rt/lib/asan/asan_interceptors.cpp:239:28

WebUI v2.5.0-beta.2:

=================================================================
==511254==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 32 byte(s) in 3 object(s) allocated from:
    #0 0x63c71e9df64a in strdup llvmSrc/compiler-rt/lib/asan/asan_interceptors.cpp:570:3
    #1 0x63c71ebc6d7c in _webui_get_file_name_from_url src/webui.c:4089:18
    #2 0x63c71ebc57d1 in _webui_serve_file src/webui.c:4259:18
    #3 0x63c71ebc371e in _webui_http_handler src/webui.c:8053:40
    #4 0x63c71ec0591c in handle_request src/civetweb/civetweb.c:15240:8
    #5 0x63c71ec02434 in handle_request_stat_log src/civetweb/civetweb.c:6665:2
    #6 0x63c71ebffe0f in process_new_connection src/civetweb/civetweb.c:19754:5
    #7 0x63c71ebfe64b in worker_thread_run src/civetweb/civetweb.c:20194:4
    #8 0x63c71ebfd9ec in worker_thread src/civetweb/civetweb.c:20255:2
    #9 0x63c71e9f3a88 in asan_thread_start(void*) llvmSrc/compiler-rt/lib/asan/asan_interceptors.cpp:239:28

SUMMARY: AddressSanitizer: 32 byte(s) leaked in 3 allocation(s).

[mochalins]

Fixed in #508