minor fix of mouse down flag handling

webui/src/components/media/annotation-box.vue

@@ -11,6 +11,7 @@
        @contextmenu.prevent
        @mousedown.prevent="click"
        @mouseup.prevent="mousedown=false"
+       @mouseleave.prevent="mousedown=false"
 
        @touchstart.prevent="click"
        @touchend.prevent="mousedown=false"