Remove legend URL query upon user interaction

This mirrors what we do for sidebar open state and prevents the URL query and the app state being out-of-sync

src/components/tree/legend/legend.js

@@ -23,6 +23,7 @@ class Legend extends React.Component {
   }
 
   showLegend() {
+    // redux state takes precedent
     if (this.props.legendOpen !== undefined) { return this.props.legendOpen; }
 
     // Our default state changes based on the size of the window or the number of items in the legend.

src/middleware/changeURL.js

@@ -81,6 +81,13 @@ export const changeURLMiddleware = (store) => (next) => (action) => {
       }
       break;
     }
+    case types.TOGGLE_LEGEND: {
+      // we treat this the same as sidebar above -- it can only be added to the URL manually
+      if ("legend" in query) {
+        query.legend = undefined;
+      }
+      break;
+    }
     case types.TOGGLE_PANEL_DISPLAY: {
       if (state.controls.panelsAvailable.length === action.panelsToDisplay.length) {
         query.d = undefined;