fix(api): Skip mapping of null values in matchers

Author: aholstenson

silo-api/src/main/java/se/l4/silo/internal/EqualsMatcherImpl.java

@@ -30,7 +30,7 @@ public V getValue()
 	@Override
 	public <NV> Matcher<NV> map(Function<V, NV> func)
 	{
-		return new EqualsMatcherImpl<>(func.apply(value));
+		return new EqualsMatcherImpl<>(value == null ? null : func.apply(value));
 	}
 
 	@Override

silo-api/src/main/java/se/l4/silo/internal/RangeMatcherImpl.java

@@ -59,9 +59,9 @@ public boolean isUpperInclusive()
 	public <NV> Matcher<NV> map(Function<T, NV> func)
 	{
 		return new RangeMatcherImpl<>(
-			func.apply(lower),
+			lower == null ? null : func.apply(lower),
 			lowerInclusive,
-			func.apply(upper),
+			upper == null ? null : func.apply(upper),
 			upperInclusive
 		);
 	}