fix: Crash when trying to read from an empty file or a directory

lib/libimhex/include/hex/helpers/file.hpp

@@ -20,7 +20,8 @@ namespace hex {
 
     class File {
     public:
-        enum class Mode {
+        enum class Mode
+        {
             Read,
             Write,
             Create
@@ -36,7 +37,9 @@ namespace hex {
         File &operator=(File &&other) noexcept;
 
 
-        [[nodiscard]] bool isValid() const { return this->m_file != nullptr; }
+        [[nodiscard]] bool isValid() const {
+            return this->m_file != nullptr && fs::exists(this->m_path) && !fs::is_directory(this->m_path);
+        }
 
         void seek(u64 offset);
         void close();

lib/libimhex/source/helpers/file.cpp

@@ -57,6 +57,8 @@ namespace hex {
         if (!isValid()) return {};
 
         auto size = numBytes ?: getSize();
+        if (size == 0) return {};
+
         std::vector<u8> bytes(size);
         auto bytesRead = fread(bytes.data(), 1, bytes.size(), this->m_file);
 
@@ -72,6 +74,9 @@ namespace hex {
 
         auto bytes = readBytes(numBytes);
 
+        if (bytes.empty())
+            return "";
+
         return { reinterpret_cast<char *>(bytes.data()), bytes.size() };
     }