fix https://github.com/gorhill/uBlock/issues/1702

platform/firefox/vapi-background.js

@@ -1785,7 +1785,7 @@ var httpObserver = {
     // the ring buffer are overwritten.
     pendingURLToIndex: new Map(),
     pendingWritePointer: 0,
-    pendingRingBuffer: new Array(32),
+    pendingRingBuffer: new Array(256),
     pendingRingBufferInit: function() {
         // Use and reuse pre-allocated PendingRequest objects = less memory
         // churning.
@@ -1812,7 +1812,7 @@ var httpObserver = {
     createPendingRequest: function(url) {
         var bucket;
         var i = this.pendingWritePointer;
-        this.pendingWritePointer = i + 1 & 31;
+        this.pendingWritePointer = i + 1 & 255;
         var preq = this.pendingRingBuffer[i];
         var si = String.fromCharCode(i);
         // Cleanup unserviced pending request