Simplify NewKey code

Author: andremacedopv

assets/key.go

@@ -59,6 +59,14 @@ func NewKey(m map[string]interface{}) (k Key, err errors.ICCError) {
 			if index != 0 {
 				keyExists = false
 			}
+		} else {
+			// Get asset type from @key
+			parts := strings.Split(k["@key"].(string), ":")
+			if len(parts) < 2 {
+				err = errors.NewCCError("cannot determine asset type from key", 400)
+				return
+			}
+			k["@assetType"] = parts[0]
 		}
 	}
 
@@ -72,18 +80,6 @@ func NewKey(m map[string]interface{}) (k Key, err errors.ICCError) {
 		k["@key"] = keyStr
 	}
 
-	// Validate if @assetType exists
-	_, typeExists := k["@assetType"].(string)
-	if !typeExists {
-		// Get asset type from @key
-		parts := strings.Split(k["@key"].(string), ":")
-		if len(parts) < 2 {
-			err = errors.NewCCError("cannot determine asset type from key", 400)
-			return
-		}
-		k["@assetType"] = parts[0]
-	}
-
 	for t := range k {
 		if t != "@key" && t != "@assetType" {
 			delete(k, t)