[blockly] Fix missing event property causes JS error (#2476)

See https://community.openhab.org/t/blockly-proposal-to-change-contextual-info-blocks/154403/27.

Signed-off-by: Stefan Höhn <mail@stefanhoehn.com>
(cherry picked from commit 32b8b88)

bundles/org.openhab.ui/web/src/assets/definitions/blockly/blocks-scripts.js

@@ -283,11 +283,11 @@ export default function defineOHBlocks_Scripts (f7, isGraalJs, scripts) {
     if (contextInfo === 'ruleUID') return ['ctx.ruleUID', javascriptGenerator.ORDER_ATOMIC]
     if (contextInfo === 'itemState' || contextInfo === 'oldItemState' || contextInfo === 'itemCommand') {
       if (type === 'asNumber') {
-        return [`parseFloat(event.${contextInfo}.toString())`, javascriptGenerator.ORDER_ATOMIC]
+        return [`event.${contextInfo} !== undefined ? parseFloat(event.${contextInfo}.toString()) : undefined`, javascriptGenerator.ORDER_ATOMIC]
       } else if (type === 'asQuantity') {
-        return [`Quantity(event.${contextInfo}.toString())`, javascriptGenerator.ORDER_ATOMIC]
+        return [`event.${contextInfo} !== undefined ? Quantity(event.${contextInfo}.toString() : undefined)`, javascriptGenerator.ORDER_ATOMIC]
       } else {
-        return [`event.${contextInfo}.toString()`, javascriptGenerator.ORDER_ATOMIC]
+        return [`event.${contextInfo}?.toString()`, javascriptGenerator.ORDER_ATOMIC]
       }
     }
     return [`event.${contextInfo}`, javascriptGenerator.ORDER_ATOMIC]