This MR is intended to fix incorrect parsing of HTTP requests when empty header values are present.
The issue is was due to asymmetric behavior of `http_parser` library, which in case of:
non-empty header values : invokes callbacks with the pointer to the start of a value
empty header values : invokes callbacks with pointer to the start of next header or section
Since HTTP server relies on this pointer (along with length of the value) to locate the end of a value, and replace the line terminators (CRLFs) with null characters, the second case needed to be handled correctly.
Closes IDFGH-1539
Closes https://github.com/espressif/esp-idf/issues/3803
38b1c93764