Fix crash in unsubscribeFromQuery

Also delete querySubscription when there is no subscription, since that
seems reasonable.

See #255.

Changelog.md

@@ -4,6 +4,8 @@ Expect active development and potentially significant breaking changes in the `0
 
 ### vNext
 
+- Bug: Fix possible crash in unsubscribeFromQuery [#260](https://github.com/apollostack/react-apollo/pull/260)
+
 ### v0.5.8
 
 - Feature: Remove nested imports for apollo-client. Making local development eaiser. [#234](https://github.com/apollostack/react-apollo/pull/234)

src/graphql.tsx

@@ -267,10 +267,13 @@ export default function graphql(
       }
 
       componentWillReceiveProps(nextProps) {
-        // if this has changed, remove data and unsubscribeFromQuery
-        if (!mapPropsToSkip(this.props) && mapPropsToSkip(nextProps)) {
-          delete this.data;
-          return this.unsubscribeFromQuery();
+        if (mapPropsToSkip(nextProps)) {
+          if (!mapPropsToSkip(this.props)) {
+            // if this has changed, remove data and unsubscribeFromQuery
+            delete this.data;
+            this.unsubscribeFromQuery();
+          }
+          return;
         }
         if (shallowEqual(this.props, nextProps)) return;
 
@@ -354,7 +357,7 @@ export default function graphql(
           if (this.querySubscription) {
             this.hasOperationDataChanged = true;
             this.data = { loading: false };
-            this.querySubscription.unsubscribe();
+            this.unsubscribeFromQuery();
             this.forceRenderChildren();
           }
           return;
@@ -416,9 +419,11 @@ export default function graphql(
       }
 
       unsubscribeFromQuery() {
-        if ((this.querySubscription as Subscription).unsubscribe) {
+        if (this.querySubscription &&
+            (this.querySubscription as Subscription).unsubscribe) {
           (this.querySubscription as Subscription).unsubscribe();
           delete this.queryObservable;
+          delete this.querySubscription;
         }
       }