Server panic on initialize message with no params

[fmcato]

Describe the bug
Got a panic sending an incomplete initialization message against an http streaming server

To Reproduce
Steps to reproduce the behavior:

curl http://localhost:8080/mcp -H "Content-Type: application/json" -H "Accept: text/event-stream, application/json" -d '{
      "jsonrpc": "2.0",
      "method": "initialize"
  }'

Expected behavior
400 Error with explanation about missing data

Logs

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x20 pc=0x6ba9f4]

goroutine 3 [running]:
github.com/modelcontextprotocol/go-sdk/mcp.(*ServerSession).initialize(0xc0000f28c0, {0x0?, 0x0?}, 0x0)
	/home/redacted/go/pkg/mod/github.com/modelcontextprotocol/go-sdk@v0.2.0/mcp/server.go:681 +0xf4
github.com/modelcontextprotocol/go-sdk/mcp.init.sessionMethod[...].func41(0xc0000a0b60?, 0xa?)
	/home/redacted/go/pkg/mod/github.com/modelcontextprotocol/go-sdk@v0.2.0/mcp/shared.go:218 +0x30
github.com/modelcontextprotocol/go-sdk/mcp.init.newMethodInfo[...].func43(0xc0000a0b60?, {0xa?, 0x900000000000000?}, {0x0?, 0x0?})
	/home/redacted/go/pkg/mod/github.com/modelcontextprotocol/go-sdk@v0.2.0/mcp/shared.go:185 +0x6f
github.com/modelcontextprotocol/go-sdk/mcp.defaultReceivingMethodHandler[...]({0x869de0, 0xc000012030}, 0xc0000f28c0, {0xc0000a0b60, 0xa}, {0x0, 0x0})
	/home/redacted/go/pkg/mod/github.com/modelcontextprotocol/go-sdk@v0.2.0/mcp/shared.go:122 +0xab
github.com/modelcontextprotocol/go-sdk/mcp.handleReceive[...]({0x869de0, 0xc000012030}, 0xc0000f28c0, 0xc0000b5300)
	/home/redacted/go/pkg/mod/github.com/modelcontextprotocol/go-sdk@v0.2.0/mcp/shared.go:137 +0x18e
github.com/modelcontextprotocol/go-sdk/mcp.(*ServerSession).handle(0xc0000f28c0, {0x869e18, 0xc000282000}, 0xc0000b5300)
	/home/redacted/go/pkg/mod/github.com/modelcontextprotocol/go-sdk@v0.2.0/mcp/server.go:660 +0x157
github.com/modelcontextprotocol/go-sdk/internal/jsonrpc2.HandlerFunc.Handle(0xc000129110?, {0x869e18?, 0xc000282000?}, 0x0?)
	/home/redacted/go/pkg/mod/github.com/modelcontextprotocol/go-sdk@v0.2.0/internal/jsonrpc2/jsonrpc2.go:91 +0x29
github.com/modelcontextprotocol/go-sdk/internal/jsonrpc2.(*Connection).handleAsync(0xc000129110)
	/home/redacted/go/pkg/mod/github.com/modelcontextprotocol/go-sdk@v0.2.0/internal/jsonrpc2/conn.go:661 +0x105
created by github.com/modelcontextprotocol/go-sdk/internal/jsonrpc2.(*Connection).acceptRequest.func2 in goroutine 23
	/home/redacted/go/pkg/mod/github.com/modelcontextprotocol/go-sdk@v0.2.0/internal/jsonrpc2/conn.go:624 +0x13f

Additional context

Haven't tried with stdio but expecting the same to happen.

[fmcato]

#209 seems related

[findleyr]

This looks like a dupe of #195, and so should be fixed at main.
Please comment if I'm missing something.