added a default constructor to Combination

MLEM/Input/Keybind.cs

@@ -390,6 +390,11 @@ namespace MLEM.Input {
                     this.InverseModifiers = this.InverseModifiers.Where(k => k != this.Key).Except(this.Modifiers).ToArray();
             }
 
+            /// <summary>
+            /// Creates a new empty combination using the default <see cref="GenericInput"/> with the <see cref="GenericInput.InputType.None"/> input type and no <see cref="Modifiers"/> or <see cref="InverseModifiers"/>.
+            /// </summary>
+            public Combination() : this(default, null, null) {}
+
             /// <summary>
             /// Returns whether this combination is currently down.
             /// See <see cref="InputHandler.IsDown"/> for more information.