Fix Android incompatibility

Author: robinst

src/main/java/org/nibor/autolink/LinkExtractor.java

@@ -66,7 +66,10 @@ private Builder() {
          * @return this builder
          */
         public Builder linkTypes(Set<LinkType> linkTypes) {
-            this.linkTypes = new HashSet<>(Objects.requireNonNull(linkTypes, "linkTypes must not be null"));
+            if (linkTypes == null) {
+                throw new NullPointerException("linkTypes must not be null");
+            }
+            this.linkTypes = new HashSet<>(linkTypes);
             return this;
         }