prevent double prompt on file drop import

frontend/src/Metamaps/PasteInput.js

@@ -20,6 +20,10 @@ const PasteInput = {
     }, false)
     window.addEventListener('drop', function(e) {
       e = e || window.event
+
+      // prevent conflict with react-dropzone file uploader
+      if (event.target.id !== 'infovis-canvas') return
+
       e.preventDefault()
       var coords = Util.pixelsToCoords(Visualize.mGraph, { x: e.clientX, y: e.clientY })
       if (e.dataTransfer.files.length > 0) {

frontend/src/components/ImportDialogBox.js

@@ -14,6 +14,7 @@ class ImportDialogBox extends Component {
   }
 
   handleFile = (files, e) => {
+    e.preventDefault() // prevent it from triggering the default drag-drop handler
     this.props.onFileAdded(files[0])
   }