fix(component): fix allowing more than allowed uploads

Author: Walker Leite

src/ic-firebase-uploader/ic-firebase-uploader.vue

@@ -93,7 +93,9 @@ export default {
          */
         this.$emit('error', new Error('maximum files reached'))
       }
-      const cFiles = Array.prototype.slice.call(files, 0, 3)
+      const cFiles = Array.prototype.slice.call(
+        files, 0, 3 - curFilesLength
+      )
       cFiles.forEach(this.uploadFile)
     },
     uploadFile(file, index, files) {