util/AllocatedString: add default constructor

src/lib/icu/Collate.cxx

@@ -88,7 +88,7 @@ IcuCollate(std::string_view a, std::string_view b) noexcept
 				     b.data(), b.size(), &code);
 
 #elif defined(_WIN32)
-	BasicAllocatedString<wchar_t> wa = nullptr, wb = nullptr;
+	BasicAllocatedString<wchar_t> wa, wb;
 
 	try {
 		wa = MultiByteToWideChar(CP_UTF8, a);

src/output/plugins/httpd/HttpdClient.cxx

@@ -136,7 +136,7 @@ bool
 HttpdClient::SendResponse() noexcept
 {
 	char buffer[1024];
-	AllocatedString allocated = nullptr;
+	AllocatedString allocated;
 	const char *response;
 
 	assert(state == State::RESPONSE);

src/util/AllocatedString.hxx

@@ -55,12 +55,13 @@ public:
 	static constexpr value_type SENTINEL = '\0';
 
 private:
-	pointer value;
+	pointer value = nullptr;
 
 	explicit BasicAllocatedString(pointer _value) noexcept
 		:value(_value) {}
 
 public:
+	BasicAllocatedString() noexcept = default;
 	BasicAllocatedString(std::nullptr_t n) noexcept
 		:value(n) {}
 
@@ -145,6 +146,7 @@ class AllocatedString : public BasicAllocatedString<char> {
 public:
 	using BasicAllocatedString::BasicAllocatedString;
 
+	AllocatedString() noexcept = default;
 	AllocatedString(BasicAllocatedString<value_type> &&src) noexcept
 		:BasicAllocatedString(std::move(src)) {}
 };