fix(2.0): incomplete chunk header (#2299)

Author: lxsmnsyc

.changeset/loose-stars-greet.md

@@ -0,0 +1,5 @@
+---
+"@solidjs/start": patch
+---
+
+fix potentially incomplete first chunk for chunk readers

packages/start/src/fns/serialization.ts

@@ -167,10 +167,14 @@ export class SerovalChunkReader {
   }
 
   async next(): Promise<{ done: true; value: undefined } | { done: false; value: string }> {
-    // Check if the buffer is empty
-    if (this.buffer.length === 0) {
+    // Check if the buffer is empty or incomplete
+    if (this.buffer.length < 12) {
       // if we are already done...
       if (this.done) {
+        // incomplete stream
+        if (this.buffer.length !== 0) {
+          throw new Error("Malformed server function stream.");
+        }
         return {
           done: true,
           value: undefined,