fix warning related to categories as an object for victory axis

src/components/victory-axis/victory-axis.js

@@ -50,7 +50,12 @@ class VictoryAxis extends React.Component {
     ...BaseProps,
     axisComponent: PropTypes.element,
     axisLabelComponent: PropTypes.element,
-    categories: PropTypes.arrayOf(PropTypes.string),
+    categories: PropTypes.oneOfType([
+      PropTypes.arrayOf(PropTypes.string),
+      PropTypes.shape({
+        x: PropTypes.arrayOf(PropTypes.string), y: PropTypes.arrayOf(PropTypes.string)
+      })
+    ]),
     crossAxis: PropTypes.bool,
     dependentAxis: PropTypes.bool,
     events: PropTypes.arrayOf(PropTypes.shape({

src/components/victory-polar-axis/victory-polar-axis.js

@@ -49,7 +49,12 @@ class VictoryPolarAxis extends React.Component {
     axisComponent: PropTypes.element,
     axisLabelComponent: PropTypes.element,
     axisValue: PropTypes.number,
-    categories: PropTypes.arrayOf(PropTypes.string),
+    categories: PropTypes.oneOfType([
+      PropTypes.arrayOf(PropTypes.string),
+      PropTypes.shape({
+        x: PropTypes.arrayOf(PropTypes.string), y: PropTypes.arrayOf(PropTypes.string)
+      })
+    ]),
     circularAxisComponent: PropTypes.element,
     circularGridComponent: PropTypes.element,
     containerComponent: PropTypes.element,

src/helpers/axis.js

@@ -197,7 +197,10 @@ export default {
   },
 
   getStringTicks(props) {
-    const { stringMap, categories } = props;
+    const { stringMap } = props;
+    const axis = this.getAxis(props);
+    const categories = Array.isArray(props.categories) ?
+      props.categories : props.categories && props.categories[axis];
     const ticksFromCategories = categories && Collection.containsOnlyStrings(categories) ?
       categories.map((tick) => stringMap[tick]) : undefined;
     const ticksFromStringMap = stringMap && values(stringMap);