Prevent c-gear on non-gen5

Closes #433

PKHeX/MainWindow/Main.cs

@@ -3929,6 +3929,8 @@ private void B_LinkInfo_Click(object sender, EventArgs e)
         }
         private void B_CGearSkin_Click(object sender, EventArgs e)
         {
+            if (SAV.Generation != 5)
+                return; // can never be too safe
             new SAV_CGearSkin().ShowDialog();
         }
         private void B_JPEG_Click(object sender, EventArgs e)