Fix(#3239) NPE, for RegexFilter creator.

Author: jaykataria1111

log4j-core-test/src/test/java/org/apache/logging/log4j/core/filter/RegexFilterTest.java

@@ -18,6 +18,7 @@
 
 import static org.hamcrest.CoreMatchers.equalTo;
 import static org.hamcrest.MatcherAssert.assertThat;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
 import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertSame;
 import static org.junit.jupiter.api.Assertions.assertTrue;
@@ -39,6 +40,13 @@ static void before() {
         StatusLogger.getLogger().setLevel(Level.OFF);
     }
 
+    @Test
+    void testRegexFilterDoesNotThrowWithAllTheParametersExceptRegexEqualNull() {
+        assertDoesNotThrow(() -> {
+            RegexFilter.createFilter(".* test .*", null, null, null, null);
+        });
+    }
+
     @Test
     void testThresholds() throws Exception {
         RegexFilter filter = RegexFilter.createFilter(".* test .*", null, false, null, null);

log4j-core/src/main/java/org/apache/logging/log4j/core/filter/RegexFilter.java

@@ -148,7 +148,8 @@ public static RegexFilter createFilter(
             LOGGER.error("A regular expression must be provided for RegexFilter");
             return null;
         }
-        return new RegexFilter(useRawMsg, Pattern.compile(regex, toPatternFlags(patternFlags)), match, mismatch);
+        return new RegexFilter(
+                Boolean.TRUE.equals(useRawMsg), Pattern.compile(regex, toPatternFlags(patternFlags)), match, mismatch);
     }
 
     private static int toPatternFlags(final String[] patternFlags)