HTTP: fix classification in some corner cases

[IvanNardi]

HTTP: fix classification in some corner cases

Initializing low->detected_protocol_stack[1] but not
low->detected_protocol_stack[0] lead to very strange errors.
Oss-fuzzer, exploiting this bug, has been able to crash the application
or to leak some memory

    ==19775==ERROR: AddressSanitizer: SEGV on unknown address (pc 0x5624c0dd1802 bp 0x5624c197e848 sp 0x7fff4b4db690 T0)
    ==19775==The signal is caused by a READ memory access.
    ==19775==Hint: this fault was caused by a dereference of a high value address (see register values below).  Disassemble the provided pc to learn which register was used.
        #0 0x5624c0dd1802 in __asan::Allocator::Deallocate(void*, unsigned long, unsigned long, __sanitizer::BufferedStackTrace*, __asan::AllocType) (/home/ivan/svnrepos/nDPI/fuzz/fuzz_ndpi_reader_with_main+0x522802) (BuildId: 9a1ed9efcaf47e345767c86520372d28e31ca1aa)
        #1 0x5624c0e53ea6 in __interceptor_free (/home/ivan/svnrepos/nDPI/fuzz/fuzz_ndpi_reader_with_main+0x5a4ea6) (BuildId: 9a1ed9efcaf47e345767c86520372d28e31ca1aa)
        #2 0x5624c0ebb474 in free_wrapper /home/ivan/svnrepos/nDPI/example/reader_util.c:330:3
        #3 0x5624c0f75561 in ndpi_free /home/ivan/svnrepos/nDPI/src/lib/ndpi_main.c:240:7
        #4 0x5624c0faa921 in ndpi_free_flow_data /home/ivan/svnrepos/nDPI/src/lib/ndpi_main.c:4915:2
        #5 0x5624c0f755ef in ndpi_free_flow /home/ivan/svnrepos/nDPI/src/lib/ndpi_main.c:8076:5
        #6 0x5624c0f755c4 in ndpi_flow_free /home/ivan/svnrepos/nDPI/src/lib/ndpi_main.c:253:5
        #7 0x5624c0eba981 in ndpi_free_flow_info_half /home/ivan/svnrepos/nDPI/example/reader_util.c:305:25
        #8 0x5624c0ecb4bc in process_ndpi_collected_info /home/ivan/svnrepos/nDPI/example/reader_util.c:1317:5
        #9 0x5624c0edca36 in packet_processing /home/ivan/svnrepos/nDPI/example/reader_util.c:1639:2
        #10 0x5624c0ed5172 in ndpi_workflow_process_packet /home/ivan/svnrepos/nDPI/example/reader_util.c:2182:10
        #11 0x5624c0e90a80 in LLVMFuzzerTestOneInput /home/ivan/svnrepos/nDPI/fuzz/fuzz_ndpi_reader.c:107:7
        #12 0x5624c0e90bbb in main /home/ivan/svnrepos/nDPI/fuzz/fuzz_ndpi_reader.c:179:17
        #13 0x7f580731f082 in __libc_start_main /build/glibc-SzIz7B/glibc-2.31/csu/../csu/libc-start.c:308:16
        #14 0x5624c0dcf52d in _start (/home/ivan/svnrepos/nDPI/fuzz/fuzz_ndpi_reader_with_main+0x52052d) (BuildId: 9a1ed9efcaf47e345767c86520372d28e31ca1aa)

    ==17492==ERROR: LeakSanitizer: detected memory leaks
    
    Direct leak of 5 byte(s) in 1 object(s) allocated from:
        #0 0x55b799b0f01e in malloc (/home/ivan/svnrepos/nDPI/fuzz/fuzz_process_packet_with_main+0x56101e) (BuildId: d2adbfb29a6eda6dc59fdfb8930d7e6496ac7b8b)
        #1 0x55b799bb3bf4 in ndpi_malloc /home/ivan/svnrepos/nDPI/src/lib/ndpi_main.c:212:46
        #2 0x55b799bb3f28 in ndpi_strdup /home/ivan/svnrepos/nDPI/src/lib/ndpi_main.c:279:13
        #3 0x55b799c8b9bf in processCertificateElements /home/ivan/svnrepos/nDPI/src/lib/protocols/tls.c:683:39
        #4 0x55b799c81e89 in processCertificate /home/ivan/svnrepos/nDPI/src/lib/protocols/tls.c:835:7
        #5 0x55b799c8d500 in processTLSBlock /home/ivan/svnrepos/nDPI/src/lib/protocols/tls.c:889:13
        #6 0x55b799ca80f1 in ndpi_search_tls_tcp /home/ivan/svnrepos/nDPI/src/lib/protocols/tls.c:1034:2
        #7 0x55b799ca3be2 in ndpi_search_tls_wrapper /home/ivan/svnrepos/nDPI/src/lib/protocols/tls.c:2475:5
        #8 0x55b799bf9345 in check_ndpi_detection_func /home/ivan/svnrepos/nDPI/src/lib/ndpi_main.c:5414:6
        #9 0x55b799bf9d57 in check_ndpi_tcp_flow_func /home/ivan/svnrepos/nDPI/src/lib/ndpi_main.c:5462:12
        #10 0x55b799bf99f7 in ndpi_check_flow_func /home/ivan/svnrepos/nDPI/src/lib/ndpi_main.c:5481:12
        #11 0x55b799c0b838 in ndpi_detection_process_packet /home/ivan/svnrepos/nDPI/src/lib/ndpi_main.c:6308:15
        #12 0x55b799b4b87e in LLVMFuzzerTestOneInput /home/ivan/svnrepos/nDPI/fuzz/fuzz_process_packet.c:29:5

    ==17511==ERROR: LeakSanitizer: detected memory leaks
    
    Direct leak of 1 byte(s) in 1 object(s) allocated from:
        #0 0x55aed645e01e in malloc (/home/ivan/svnrepos/nDPI/fuzz/fuzz_process_packet_with_main+0x56101e) (BuildId: d2adbfb29a6eda6dc59fdfb8930d7e6496ac7b8b)
        #1 0x55aed6502bf4 in ndpi_malloc /home/ivan/svnrepos/nDPI/src/lib/ndpi_main.c:212:46
        #2 0x55aed6502f28 in ndpi_strdup /home/ivan/svnrepos/nDPI/src/lib/ndpi_main.c:279:13
        #3 0x55aed65ea0c6 in processClientServerHello /home/ivan/svnrepos/nDPI/src/lib/protocols/tls.c:2153:34
        #4 0x55aed65dbe77 in processTLSBlock /home/ivan/svnrepos/nDPI/src/lib/protocols/tls.c:867:5
        #5 0x55aed65f70f1 in ndpi_search_tls_tcp /home/ivan/svnrepos/nDPI/src/lib/protocols/tls.c:1034:2
        #6 0x55aed65f2be2 in ndpi_search_tls_wrapper /home/ivan/svnrepos/nDPI/src/lib/protocols/tls.c:2475:5
        #7 0x55aed6548345 in check_ndpi_detection_func /home/ivan/svnrepos/nDPI/src/lib/ndpi_main.c:5414:6
        #8 0x55aed6548d57 in check_ndpi_tcp_flow_func /home/ivan/svnrepos/nDPI/src/lib/ndpi_main.c:5462:12
        #9 0x55aed65489f7 in ndpi_check_flow_func /home/ivan/svnrepos/nDPI/src/lib/ndpi_main.c:5481:12
        #10 0x55aed655a838 in ndpi_detection_process_packet /home/ivan/svnrepos/nDPI/src/lib/ndpi_main.c:6308:15
        #11 0x55aed649a87e in LLVMFuzzerTestOneInput /home/ivan/svnrepos/nDPI/fuzz/fuzz_process_packet.c:29:5

See: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=49844
See: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=49842
See: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=49906
See: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=49915

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