save_data: Fix save data list back button. (#1003)

* save_data: Fix save data list back button.

* common: Add more null checks in CString.

Co-authored-by: Vinicius Rangel <me@viniciusrangel.dev>

---------

Co-authored-by: Vinicius Rangel <me@viniciusrangel.dev>

src/common/cstring.h

@@ -9,6 +9,9 @@
 
 namespace Common {
 
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wtautological-undefined-compare"
+
 /**
  * @brief A null-terminated string with a fixed maximum length
  *        This class is not meant to be used as a general-purpose string class
@@ -29,20 +32,27 @@ public:
     explicit CString(const CString<M>& other)
         requires(M <= N)
     {
+        if (this == nullptr) {
+            return;
+        }
         std::ranges::copy(other.begin(), other.end(), data);
     }
 
     void FromString(const std::basic_string_view<T>& str) {
+        if (this == nullptr) {
+            return;
+        }
         size_t p = str.copy(data, N - 1);
         data[p] = '\0';
     }
 
     void Zero() {
+        if (this == nullptr) {
+            return;
+        }
         std::ranges::fill(data, 0);
     }
 
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wtautological-undefined-compare"
     explicit(false) operator std::basic_string_view<T>() const {
         if (this == nullptr) {
             return {};
@@ -70,21 +80,32 @@ public:
         }
         return std::basic_string_view<T>{data};
     }
-#pragma clang diagnostic pop
 
     char* begin() {
+        if (this == nullptr) {
+            return nullptr;
+        }
         return data;
     }
 
     const char* begin() const {
+        if (this == nullptr) {
+            return nullptr;
+        }
         return data;
     }
 
     char* end() {
+        if (this == nullptr) {
+            return nullptr;
+        }
         return data + N;
     }
 
     const char* end() const {
+        if (this == nullptr) {
+            return nullptr;
+        }
         return data + N;
     }
 
@@ -127,7 +148,10 @@ public:
         }
     };
 };
+
 static_assert(sizeof(CString<13>) == sizeof(char[13])); // Ensure size still matches a simple array
 static_assert(std::weakly_incrementable<CString<13>::Iterator>);
 
+#pragma clang diagnostic pop
+
 } // namespace Common

src/core/libraries/save_data/dialog/savedatadialog_ui.cpp

@@ -620,7 +620,7 @@ void SaveDialogUi::DrawList() {
         SetCursorPosX(GetContentRegionAvail().x - button_size.x);
         if (Button(back, button_size)) {
             result->dir_name.clear();
-            Finish(ButtonId::INVALID);
+            Finish(ButtonId::INVALID, Result::USER_CANCELED);
         }
         if (IsKeyPressed(ImGuiKey_GamepadFaceRight)) {
             SetItemCurrentNavFocus();