fix(runtime): Passing in invalid date to "Date To String" node causes node scope to fail (#75)

packages/noodl-runtime/src/nodes/std-library/datetostring.js

@@ -31,8 +31,6 @@ const DateToStringNode = {
 
         this._internal.currentInput = _value;
         this._format();
-        this.flagOutputDirty('currentValue');
-        this.sendSignalOnOutput('inputChanged');
       }
     }
   },
@@ -49,10 +47,16 @@ const DateToStringNode = {
       type: 'signal',
       displayName: 'Date Changed',
       group: 'Signals'
+    },
+    onError: {
+      type: 'signal',
+      displayName: 'Invalid Date',
+      group: 'Signals'
     }
   },
   methods: {
     _format() {
+      try {
         const t = this._internal.currentInput;
         const format = this._internal.formatString;
         const date = ('0' + t.getDate()).slice(-2);
@@ -73,6 +77,15 @@ const DateToStringNode = {
           .replace(/\{hours\}/g, hours)
           .replace(/\{minutes\}/g, minutes)
           .replace(/\{seconds\}/g, seconds);
+      } catch (error) {
+        // Set the output to be blank, makes it easier to handle.
+        this._internal.dateString = '';
+        this.flagOutputDirty('onError');
+      }
+
+      // Flag that the value have changed
+      this.flagOutputDirty('currentValue');
+      this.sendSignalOnOutput('inputChanged');
     }
   }
 };