introduce single-param null-aware of(item)

platform/util/src/com/intellij/util/containers/JBIterable.java

@@ -148,6 +148,14 @@ public abstract class JBIterable<E> implements Iterable<E> {
     };
   }
 
+  /**
+   * Returns a {@code JBIterable} containing the one {@code element}.
+   */
+  @NotNull
+  public static <E> JBIterable<E> of(@Nullable E element) {
+    return element == null ? JBIterable.<E>empty() : from(Collections.singletonList(element));
+  }
+
   /**
    * Returns a {@code JBIterable} containing {@code elements} in the specified order.
    */