AK+Userland: Remove nullability feature for the ByteBuffer type

Nobody seems to use this particular feature, in fact there were some
bugs which were uncovered by removing operator bool.

Userland/Applications/HexEditor/HexEditor.cpp

@@ -563,11 +563,6 @@ int HexEditor::find_and_highlight(ByteBuffer& needle, int start)
     if (m_buffer.is_empty())
         return -1;
 
-    if (needle.is_null()) {
-        dbgln("needle is null");
-        return -1;
-    }
-
     auto raw_offset = memmem(m_buffer.data() + start, m_buffer.size(), needle.data(), needle.size());
     if (raw_offset == NULL)
         return -1;

Userland/Applications/HexEditor/HexEditorWidget.cpp

@@ -189,7 +189,7 @@ void HexEditorWidget::initialize_menubar(GUI::Menubar& menubar)
     }));
 
     edit_menu.add_action(GUI::Action::create("Find &Next", { Mod_None, Key_F3 }, Gfx::Bitmap::load_from_file("/res/icons/16x16/find-next.png"), [&](const GUI::Action&) {
-        if (m_search_text.is_empty() || m_search_buffer.is_empty() || m_search_buffer.is_null()) {
+        if (m_search_text.is_empty() || m_search_buffer.is_empty()) {
             GUI::MessageBox::show(window(), "Nothing to search for", "Not found", GUI::MessageBox::Type::Warning);
             return;
         }

Userland/Libraries/LibCore/IODevice.cpp

@@ -33,8 +33,6 @@ const char* IODevice::error_string() const
 int IODevice::read(u8* buffer, int length)
 {
     auto read_buffer = read(length);
-    if (read_buffer.is_null())
-        return 0;
     memcpy(buffer, read_buffer.data(), length);
     return read_buffer.size();
 }
@@ -151,8 +149,6 @@ ByteBuffer IODevice::read_all()
         }
         data.append((const u8*)read_buffer, nread);
     }
-    if (data.is_empty())
-        return {};
     return ByteBuffer::copy(data.data(), data.size());
 }
 

Userland/Libraries/LibGemini/Job.cpp

@@ -110,7 +110,7 @@ void Job::on_socket_connected()
             auto read_size = 64 * KiB;
 
             auto payload = receive(read_size);
-            if (!payload) {
+            if (payload.is_empty()) {
                 if (eof()) {
                     finish_up();
                     return IterationDecision::Break;

Userland/Libraries/LibHTTP/Job.cpp

@@ -283,7 +283,7 @@ void Job::on_socket_connected()
             }
 
             auto payload = receive(read_size);
-            if (!payload) {
+            if (payload.is_empty()) {
                 if (eof()) {
                     finish_up();
                     return IterationDecision::Break;

Userland/Libraries/LibTLS/ClientHandshake.cpp

@@ -474,9 +474,7 @@ ssize_t TLSv12::handle_payload(ReadonlyBytes vbuffer)
             }
             break;
         case Finished:
-            if (m_context.cached_handshake) {
-                m_context.cached_handshake.clear();
-            }
+            m_context.cached_handshake.clear();
             if (m_context.handshake_messages[10] >= 1) {
                 dbgln("unexpected finished message");
                 payload_res = (i8)Error::UnexpectedMessage;

Userland/Libraries/LibWeb/CSS/Parser/DeprecatedCSSParser.cpp

@@ -431,7 +431,7 @@ public:
         if (type != CSS::Selector::SimpleSelector::Type::Universal) {
             while (is_valid_selector_char(peek()))
                 buffer.append(consume_one());
-            PARSE_VERIFY(!buffer.is_null());
+            PARSE_VERIFY(!buffer.is_empty());
         }
 
         auto value = String::copy(buffer);

Userland/Libraries/LibWeb/Loader/Resource.h

@@ -42,7 +42,7 @@ public:
     bool is_failed() const { return m_failed; }
     const String& error() const { return m_error; }
 
-    bool has_encoded_data() const { return !m_encoded_data.is_null(); }
+    bool has_encoded_data() const { return !m_encoded_data.is_empty(); }
 
     const URL& url() const { return m_request.url(); }
     const ByteBuffer& encoded_data() const { return m_encoded_data; }

Userland/Libraries/LibWeb/XHR/XMLHttpRequest.cpp

@@ -47,7 +47,7 @@ void XMLHttpRequest::fire_progress_event(const String& event_name, u64 transmitt
 
 String XMLHttpRequest::response_text() const
 {
-    if (m_response_object.is_null())
+    if (m_response_object.is_empty())
         return {};
     return String::copy(m_response_object);
 }

Userland/Services/FileOperation/main.cpp

@@ -143,7 +143,7 @@ int perform_copy(const String& source, const String& destination)
         while (true) {
             print_progress();
             auto buffer = source_file.read(65536);
-            if (buffer.is_null())
+            if (buffer.is_empty())
                 break;
             if (!destination_file.write(buffer)) {
                 report_warning(String::formatted("Failed to write to destination file: {}", destination_file.error_string()));

Userland/Services/LookupServer/MulticastDNS.cpp

@@ -168,7 +168,7 @@ Vector<DNSAnswer> MulticastDNS::lookup(const DNSName& name, DNSRecordType record
         }
 
         auto buffer = receive(1024);
-        if (!buffer)
+        if (buffer.is_empty())
             return {};
         auto optional_packet = DNSPacket::from_raw_packet(buffer.data(), buffer.size());
         if (!optional_packet.has_value()) {

Userland/Services/WebServer/Client.cpp

@@ -41,7 +41,7 @@ void Client::start()
 {
     m_socket->on_ready_to_read = [this] {
         auto raw_request = m_socket->read_all();
-        if (raw_request.is_null()) {
+        if (raw_request.is_empty()) {
             die();
             return;
         }

Userland/Utilities/du.cpp

@@ -106,7 +106,8 @@ int parse_args(int argc, char** argv, Vector<String>& files, DuOption& du_option
         auto file = Core::File::construct(exclude_from);
         bool success = file->open(Core::OpenMode::ReadOnly);
         VERIFY(success);
-        if (const auto buff = file->read_all()) {
+        const auto buff = file->read_all();
+        if (!buff.is_empty()) {
             String patterns = String::copy(buff, Chomp);
             du_option.excluded_patterns.append(patterns.split('\n'));
         }