Improve HandshakeSessionHandler#cleanVhost()

proxy/src/main/java/com/velocitypowered/proxy/connection/client/HandshakeSessionHandler.java

@@ -139,7 +139,7 @@ public class HandshakeSessionHandler implements MinecraftSessionHandler {
 
     // If we connect through an SRV record, there will be a period at the end (DNS usually elides
     // this ending octet).
-    if (cleaned.endsWith(".")) {
+    if (!cleaned.isEmpty() && cleaned.charAt(cleaned.length() - 1) == '.') {
       cleaned = cleaned.substring(0, cleaned.length() - 1);
     }
     return cleaned;

proxy/src/test/java/com/velocitypowered/proxy/connection/client/HandshakeSessionHandlerTest.java

@@ -11,20 +11,32 @@ class HandshakeSessionHandlerTest {
   @Test
   void cleanVhostHandlesGoodHostname() {
     assertEquals("localhost", cleanVhost("localhost"));
+    assertEquals("mc.example.com", cleanVhost("mc.example.com"));
   }
 
   @Test
   void cleanVhostHandlesTrailingOctet() {
     assertEquals("localhost", cleanVhost("localhost."));
+    assertEquals("mc.example.com", cleanVhost("mc.example.com."));
   }
 
   @Test
   void cleanVhostHandlesForge() {
     assertEquals("localhost", cleanVhost("localhost" + HANDSHAKE_HOSTNAME_TOKEN));
+    assertEquals("mc.example.com", cleanVhost("mc.example.com" + HANDSHAKE_HOSTNAME_TOKEN));
   }
 
   @Test
   void cleanVhostHandlesOctetsAndForge() {
     assertEquals("localhost", cleanVhost("localhost." + HANDSHAKE_HOSTNAME_TOKEN));
+    assertEquals("mc.example.com", cleanVhost("mc.example.com." + HANDSHAKE_HOSTNAME_TOKEN));
+  }
+
+  @Test
+  void cleanVhostHandlesEmptyHostnames() {
+    assertEquals("", cleanVhost(""));
+    assertEquals("", cleanVhost(HANDSHAKE_HOSTNAME_TOKEN));
+    assertEquals("", cleanVhost("."));
+    assertEquals("", cleanVhost("." + HANDSHAKE_HOSTNAME_TOKEN));
   }
 }