add checks for message channel usage in web runtime (#142)

Author: gvkhna

packages/runtime/src/Context.ts

@@ -92,15 +92,19 @@ class NodejsWaitingRequestCounter {
 
   public increase (): void {
     if (this.count === 0) {
-      this.refHandle.ref()
+      if (this.refHandle.ref) {
+        this.refHandle.ref()
+      }
     }
     this.count++
   }
 
   public decrease (): void {
     if (this.count === 0) return
     if (this.count === 1) {
-      this.refHandle.unref()
+      if (this.refHandle.unref) {
+        this.refHandle.unref()
+      }
     }
     this.count--
   }