this commit fix bug if i try to put null value for one fact

easy-rules-core/src/main/java/org/jeasy/rules/core/RuleProxy.java

@@ -146,7 +146,7 @@ private List<Object> getActualParameters(Method method, Facts facts) {
             if (annotations.length == 1) {
                 String factName = ((Fact) (annotations[0])).value(); //validated upfront.
                 Object fact = facts.get(factName);
-                if (fact == null) {
+                if (fact == null && !facts.asMap().containsKey(factName)) {
                     throw new NoSuchFactException(format("No fact named '%s' found in known facts: \n%s", factName, facts), factName);
                 }
                 actualParameters.add(fact);

easy-rules-core/src/test/java/org/jeasy/rules/core/NullFactAnnotationParameterTest.java

@@ -0,0 +1,63 @@
+package org.jeasy.rules.core;
+
+import org.jeasy.rules.annotation.Action;
+import org.jeasy.rules.annotation.Condition;
+import org.jeasy.rules.annotation.Fact;
+import org.jeasy.rules.annotation.Rule;
+import org.jeasy.rules.api.Facts;
+import org.jeasy.rules.api.Rules;
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.util.Map;
+
+/**
+ * Null value in facts must be accepted, this is not same thing that fact missing
+ */
+public class NullFactAnnotationParameterTest extends AbstractTest {
+
+    @Test
+    public void testNullFact() {
+        Rules rules = new Rules();
+        rules.register(new AnnotatedParametersRule());
+
+        Facts facts = new Facts();
+        facts.put("fact1", new Object());
+        facts.put("fact2", null);
+
+        Map<org.jeasy.rules.api.Rule, Boolean> results = rulesEngine.check(rules, facts);
+
+        for (boolean b : results.values()) {
+            Assert.assertTrue(b);
+        }
+    }
+
+    @Test
+    public void testMissingFact() {
+        Rules rules = new Rules();
+        rules.register(new AnnotatedParametersRule());
+
+        Facts facts = new Facts();
+        facts.put("fact1", new Object());
+
+        Map<org.jeasy.rules.api.Rule, Boolean> results = rulesEngine.check(rules, facts);
+
+        for (boolean b : results.values()) {
+            Assert.assertFalse(b);
+        }
+    }
+
+    @Rule
+    public class AnnotatedParametersRule {
+
+        @Condition
+        public boolean when(@Fact("fact1") Object fact1, @Fact("fact2") Object fact2) {
+            return fact1 != null && fact2 == null;
+        }
+
+        @Action
+        public void then(@Fact("fact1") Object fact1, @Fact("fact2") Object fact2) {
+        }
+
+    }
+}