Fix invalid callback return value preventing canvas redraw (#343)

* Fix invalid callback prevents redraw

When widget.mouse() is incorrectly implemented (no return value), it evaluates as falsy and prevents canvas redraw.

Changes default behaviour to ignore the return value when nullish.

* Fix pointermove for custom widget outside nodes

Events are now also sent when the pointer moves outside the bounds of the node.

src/LGraphCanvas.ts

@@ -2804,6 +2804,18 @@ export class LGraphCanvas {
 
     e.dragging = this.last_mouse_dragging
 
+    if (this.node_widget) {
+      // Legacy widget mouse callbacks for pointermove events
+      const [node, widget] = this.node_widget
+
+      if (widget?.mouse) {
+        const x = e.canvasX - node.pos[0]
+        const y = e.canvasY - node.pos[1]
+        const result = widget.mouse(e, [x, y], node)
+        if (result != null) this.dirty_canvas = result
+      }
+    }
+
     /** See {@link state}.{@link LGraphCanvasState.hoveringOver hoveringOver} */
     let underPointer = CanvasItem.Nothing
     // get node over
@@ -2956,15 +2968,6 @@ export class LGraphCanvas {
         // Resize corner
         if (node.inResizeCorner(e.canvasX, e.canvasY)) {
           underPointer |= CanvasItem.ResizeSe
-        } else if (this.node_widget) {
-          // Legacy widget mouse callbacks for pointermove events
-          const widget = this.node_widget[1]
-
-          if (widget?.mouse) {
-            const x = e.canvasX - node.pos[0]
-            const y = e.canvasY - node.pos[1]
-            this.dirty_canvas = widget.mouse(e, [x, y], node)
-          }
         }
       } else {
         // Not over a node