common: Don't terminate on null character in UrlDecode

The previous behavior was the result of casting the result returned from the libevent function evhttp_uridecode to std:string but this was probably not intended.

src/common/url.cpp

@@ -25,11 +25,6 @@ std::string UrlDecode(std::string_view url_encoded)
             // Only if there is no error and the pointer is set to the end of
             // the string, we can be sure both characters were valid hex
             if (ec == std::errc{} && p == url_encoded.data() + i + 3) {
-                // A null character terminates the string
-                if (decoded_value == 0) {
-                    return res;
-                }
-
                 res += static_cast<char>(decoded_value);
                 // Next two characters are part of the percent encoding
                 i += 2;

src/test/common_url_tests.cpp

@@ -63,8 +63,10 @@ BOOST_AUTO_TEST_CASE(decode_lowercase_hex_test) {
 }
 
 BOOST_AUTO_TEST_CASE(decode_internal_nulls_test) {
-    BOOST_CHECK_EQUAL(UrlDecode("%00%00x%00%00"), "");
+    std::string result1{"\0\0x\0\0", 5};
-    BOOST_CHECK_EQUAL(UrlDecode("abc%00%00"), "abc");
+    BOOST_CHECK_EQUAL(UrlDecode("%00%00x%00%00"), result1);
+    std::string result2{"abc\0\0", 5};
+    BOOST_CHECK_EQUAL(UrlDecode("abc%00%00"), result2);
 }
 
 BOOST_AUTO_TEST_SUITE_END()