Reset send information and better state check before cancel.

src/components/Chat.vue

@@ -1573,7 +1573,9 @@ export default {
 
     cancelSendAttachment() {
       this.$refs.attachment.value = null;
-      this.cancelSendAttachments();
+      if (this.sendingStatus != this.sendStatuses.INITIAL) {
+        this.cancelSendAttachments();
+      }
       this.currentFileInputs = null;
       this.attachmentCaption = undefined;
       this.currentSendError = null;

src/components/sendAttachmentsMixin.js

@@ -123,6 +123,8 @@ export default {
         })
         .then(() => {
           this.sendingStatus = this.sendStatuses.SENT;
+          this.sendingAttachments = [];
+          this.sendingRootEventId = null;
         })
         .catch((err) => {
           console.error("ERROR", err);