fix: Resolver returns empty string for Pattern#group

pom.xml

@@ -5,7 +5,7 @@
 
     <groupId>net.ranides</groupId>
     <artifactId>assira</artifactId>
-    <version>0.68.4</version>
+    <version>0.68.5</version>
     <packaging>jar</packaging>
 
     <name>assira</name>

src/main/java/net/ranides/assira/reflection/Resolver.java

@@ -13,6 +13,7 @@ import java.util.Map;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 import net.ranides.assira.collection.ArrayUtils;
+import net.ranides.assira.generic.ValueUtils;
 import net.ranides.assira.text.Strings;
 
 /**
@@ -181,7 +182,7 @@ public final class Resolver implements Serializable {
         @Override
         public Object get(Object context) {
             if(context instanceof Matcher) {
-                return ((Matcher)context).group(index);
+                return ValueUtils.or(((Matcher)context).group(index), "");
             }
             if(context instanceof CharSequence) {
                 return ((CharSequence)context).charAt(index);