fix(combineLatest): Don't mutate array of observables passed to (#2276)

combineLatest

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src/operator/combineLatest.ts

@@ -79,7 +79,7 @@ export function combineLatest<T, R>(this: Observable<T>, ...observables: Array<O
   // if the first and only other argument besides the resultSelector is an array
   // assume it's been called with `combineLatest([obs1, obs2, obs3], project)`
   if (observables.length === 1 && isArray(observables[0])) {
-    observables = <any>observables[0];
+    observables = (<any>observables[0]).slice();
   }
 
   observables.unshift(this);