fixed loading box to center correctly

src/pages/Upload.vue

@@ -22,9 +22,9 @@
       </section>
       <section
         v-if="supportedExtensions.length == 0"
-        class="q-pa-sm q-pa-md col-xs-10 offset-xs-1
-          col-sm-6 offset-sm-3 col-md-8 offset-md-2
-          col-lg-6 offset-lg-3 p-1 mat-shadowed-box"
+        class="q-pa-sm q-pa-md col-xs-12
+          col-sm-8 col-md-8
+          col-lg-6 mat-shadowed-box"
       >
         <q-circular-progress
           indeterminate