fix(edge): Wrapped setting of dropEffect in try/catch block, as i…

…t causes errors in MS Edge/IE11 (#258)

* wrapped setting of `dropEffect` in `try/catch`, as it causes errors in MS Edge/IE11

Closes #248

src/index.js

@@ -68,7 +68,11 @@ class Dropzone extends React.Component {
   onDragOver(e) {
     e.preventDefault();
     e.stopPropagation();
-    e.dataTransfer.dropEffect = 'copy'; // eslint-disable-line no-param-reassign
+    try {
+      e.dataTransfer.dropEffect = 'copy'; // eslint-disable-line no-param-reassign
+    } catch (err) {
+      // continue regardless of error
+    }
     return false;
   }