support "when I receive" hat blocks with (empty) data when clicking the green flag button in the IDE

HISTORY.md

@@ -12,7 +12,7 @@
     * export block definitions from inside the block editor
     * embed blocks into costume metadata to be shared as image file
     * exported script pics now always include the actual blocks, which can be extracted from the image inside Snap!
-    * added green flag symbol to "when I receive" dropdown menu
+    * added green flag symbol to "when I receive" dropdown menu, support when clicking the green flag button in the IDE
     * added "combinations" primitive to the palette
     * new POSITION primitive reporter in the MOTION category
     * new MOUSE POSITION primitive reporter in the SENSING category
@@ -64,6 +64,7 @@
 * updated sw.js with new costumes
 * updated sw.js with new libraries
 * blocks, objects: added green flag symbol to "when I receive" dropdown menu
+* objects: support "when I receive" hat blocks with (empty) data when clicking the green flag button in the IDE
 
 ### 2022-07-18
 * German translation update: Changed translation of "point in direction" to "setze Richtung auf ... Grad"

src/objects.js

@@ -8886,13 +8886,29 @@ StageMorph.prototype.fireGreenFlagEvent = function () {
     this.removeAllClones();
     this.children.concat(this).forEach(morph => {
         if (isSnapObject(morph)) {
-            morph.allHatBlocksFor('__shout__go__').forEach(block =>
+            morph.allHatBlocksFor('__shout__go__').forEach(block => {
+                var varName, varFrame;
+
+                if (block.selector === 'receiveMessage') {
+                    varName = block.inputs()[1].evaluate()[0];
+                    if (varName) {
+                        varFrame = new VariableFrame();
+                        varFrame.addVar(varName, ''); // empty
+                    }
+                }
+
                 procs.push(this.threads.startProcess(
                     block,
                     morph,
-                    this.isThreadSafe
-                ))
-            );
+                    this.isThreadSafe,
+                    null, // exportResult (bool)
+                    null, // callback
+                    null, // isClicked
+                    null, // rightAway
+                    null, // atomic
+                    varFrame
+                ));
+            });
         }
     });
     if (ide) {