[Glitch] make draggingOver state off correctly

Port d6433b3931 to glitch-soc

app/javascript/flavours/glitch/features/ui/index.js

@@ -182,6 +182,7 @@ export default class UI extends React.Component {
     e.preventDefault();
 
     this.setState({ draggingOver: false });
+    this.dragTargets = [];
 
     if (e.dataTransfer && e.dataTransfer.files.length === 1) {
       this.props.dispatch(uploadCompose(e.dataTransfer.files));