QCParts: Check if signatures are available

WPinternals/Models/QualcommPartition.cs

@@ -160,6 +160,8 @@ namespace WPinternals
                 }
             }
 
+            if (Signatures.Count > 0)
+            {
                 byte[] RootCertificate = Signatures[^1];
 
                 for (int i = 0; i < Signatures.Count; i++)
@@ -183,3 +185,4 @@ namespace WPinternals
             }
         }
     }
+}