Fix selectedItem not returning currently selected value (fixes AssistoLab#208)

Author: iwb-kevin-hirsch

DropDown/src/DropDown.swift

@@ -955,7 +955,7 @@ extension DropDown {
 	and `cellConfiguration` implicitly calls `reloadAllComponents()`.
 	*/
 	public func reloadAllComponents() {
-		DispatchQueue.main.async {
+		DispatchQueue.executeOnMainThread {
 			self.tableView.reloadData()
 			self.setNeedsUpdateConstraints()
 		}
@@ -1184,3 +1184,13 @@ extension DropDown {
 	}
 
 }
+
+private extension DispatchQueue {
+	static func executeOnMainThread(_ closure: @escaping Closure) {
+		if Thread.isMainThread {
+			closure()
+		} else {
+			main.async(execute: closure)
+		}
+	}
+}