fix: nil slices and maps in params

[ankittk]

fix: ensure JSON-RPC 2.0 compliance for nil slices and maps

The Params() function was returning null for nil slices and nil maps,
which violates the JSON-RPC 2.0 specification that requires params
to be either an array or an object.

• Fix nil slice handling: convert to empty array [] instead of null
• Fix nil map handling: convert to empty object {} instead of null
• Added tests for nil slice/map scenarios
• Maintain backward compatibility for all existing functionality

Before

var nilSlice []int = nil
result := Params(nilSlice)
// Returns: null (invalid JSON-RPC)

var nilMap map[string]interface{} = nil  
result := Params(nilMap)
// Returns: null (invalid JSON-RPC)

After

var nilSlice []int = nil
result := Params(nilSlice)
// Returns: [] (empty array - valid JSON-RPC)

var nilMap map[string]interface{} = nil
result := Params(nilMap)  
// Returns: {} (empty object - valid JSON-RPC)

[ankittk]

@ybbus How to get this reviewed?