do not add questions to derivation chain, they do not propagate truth value...

do not add questions to derivation chain, they do not propagate truth value and it will lead to isses if a question is used as the task. todo: also analyze why second question does not work on issue30.

nars_core_java/nars/storage/Memory.java

@@ -317,7 +317,7 @@ public class Memory {
             }
             Stamp stamp = task.getSentence().getStamp();
             ArrayList<Term> chain = stamp.getChain();
-            if (currentBelief != null) {
+            if (currentBelief != null && currentBelief.isJudgment()) {
                 if(chain.contains(currentBelief.getContent())) {
                     chain.remove(currentBelief.getContent());
                 }
@@ -325,14 +325,14 @@ public class Memory {
                 
             }
             //workaround for single premise task issue:
-            if(currentBelief == null && single && currentTask != null) {
+            if(currentBelief == null && single && currentTask != null && currentTask.getSentence().isJudgment()) {
                 if(chain.contains(currentTask.getContent())) {
                     chain.remove(currentTask.getContent());
                 }
                 stamp.addToChain(currentTask.getContent());
             }
             //end workaround
-            if (currentTask != null && !single) {
+            if (currentTask != null && !single && currentTask.getSentence().isJudgment()) {
                 if(chain.contains(currentTask.getContent())) {
                     chain.remove(currentTask.getContent());
                 }
@@ -340,7 +340,7 @@ public class Memory {
             }
             if (!revised) { //its a inference rule, we have to do the derivation chain check to hamper cycles
                 for (Term chain1 : chain) {
-                    if (task.getContent() == chain1) {
+                    if (task.getSentence().isJudgment() && task.getContent().equals(chain1)) {
                         recorder.append("!!! Cyclic Reasoning detected: " + task + "\n");
                         return;
                     }