Merge pull request #13038 from Ferdi265/fix-rvz-clang-ub

RVZ: Fix undefined behaviour when copying 0 bytes to a null pointer

Source/Core/DiscIO/WIABlob.cpp

@@ -765,7 +765,14 @@ bool WIARVZFileReader<RVZ>::Chunk::Decompress()
     const size_t bytes_to_move = m_out.bytes_written - m_out_bytes_used_for_exceptions;
 
     DecompressionBuffer in{std::vector<u8>(bytes_to_move), bytes_to_move};
-    std::memcpy(in.data.data(), m_out.data.data() + m_out_bytes_used_for_exceptions, bytes_to_move);
+
+    // Copying to a null pointer is undefined behaviour, so only copy when we
+    // actually have data to copy.
+    if (bytes_to_move > 0)
+    {
+      std::memcpy(in.data.data(), m_out.data.data() + m_out_bytes_used_for_exceptions,
+                  bytes_to_move);
+    }
 
     m_out.bytes_written = m_out_bytes_used_for_exceptions;