FIX: off-by-one error when identifying patch/Rack version by reading the magic sequence of a zstd-compressed patch (#871)

* FIX: off-by-one error when identifying the patch/Rack version by reading the magic sequence of a zstd-compressed patch.

* review: using array of uint8_t instead of char[] for recognizing magic number of an zstd archive

* review: explicit size of the zstd magic number array

src/CardinalPlugin.cpp

@@ -1104,7 +1104,7 @@ protected:
         rack::system::removeRecursively(fAutosavePath);
         rack::system::createDirectories(fAutosavePath);
 
-        static constexpr const char zstdMagic[] = "\x28\xb5\x2f\xfd";
+        static constexpr const uint8_t zstdMagic[4] = { 0x28, 0xb5, 0x2f, 0xfd };
 
         if (std::memcmp(data.data(), zstdMagic, sizeof(zstdMagic)) != 0)
         {