Add null check for errorType

 Add null check for errorType to prevent false positive.

Author: daMatz

Attacks/src/main/java/de/rub/nds/tlsattacker/attacks/impl/BleichenbacherAttacker.java

@@ -107,7 +107,7 @@ public State executeTlsFlow(BleichenbacherWorkflowType type, byte[] encryptedPMS
     @Override
     public Boolean isVulnerable() {
         errorType = getEqualityError();
-        if (errorType != EqualityError.NONE) {
+        if (errorType != null && errorType != EqualityError.NONE) {
             vulnerableType = config.getWorkflowType();
             return true;
         }