fix two step write bug cause of write 0 length data

src/channel.js

@@ -401,12 +401,12 @@ export class Channel {
     this.#readPointerCache = this.#getReadPointer();
 
 
-    if (!this.#isAbleToWrite(size)) {
+    if (!this.#isAbleToWrite(size) || size == 0) {
       return [];
     }
 
     if (this.#writePhase != WRITE_PHASE.NO_STEP_WRITE)
-      throw new Error("Unable to call multiple writeStep1() consecutively")
+      throw new Error("Unable to call multiple writeStep1()");
 
     this.#writePhase = WRITE_PHASE.WAIT_CALLER_WRITE;
     let schedule = this.#cpySchedule(size);
@@ -431,12 +431,13 @@ export class Channel {
 
     if (endPos != undefined)
       this.#writePhaseEndPos = endPos;
+
     return buffers;
   }
 
   writeStep2() {
     if (this.#writePhase != WRITE_PHASE.WAIT_CALLER_WRITE)
-      return;
+      throw new Error("Have to call writeStep1() first")
     this.#writePointerUpdate(this.#writePhaseEndPos);
     this.#writePhase = WRITE_PHASE.NO_STEP_WRITE;
   }