Fixed Windows/MSVC compilation.

source/mijin/io/stream.cpp

@@ -2,6 +2,7 @@
 #include "./stream.hpp"
 
 #include <algorithm>
+#include <array>
 #include <cassert>
 #include <limits>
 
@@ -143,6 +144,9 @@ StreamError FileStream::open(const char* path, FileOpenMode mode_)
         case FileOpenMode::READ_WRITE:
             modeStr = "r+b";
             break;
+		default:
+			MIJIN_FATAL("Invalid value for mode.");
+			return StreamError::UNKNOWN_ERROR;
     }
     handle = std::fopen(path, modeStr); // NOLINT(cppcoreguidelines-owning-memory)
     if (!handle && mode_ == FileOpenMode::READ_WRITE) {