Can't compile async function with library injection disabled

Sample input code:
```js
(async function(){})()
```
Expected output: it compiles
Actual output:
```
liam$ java -jar /usr/lib/node_modules/google-closure-compiler/compiler.jar --inject_libraries=false <<< '(async function(){})()'
The compiler is waiting for input via stdin.
java.lang.RuntimeException: INTERNAL COMPILER ERROR.
Please report this problem.

Unexpected variable $jscomp
Node(NAME $jscomp): stdin:1:17
(async function(){})()
Parent(GETPROP): stdin:1:17
(async function(){})()

at com.google.javascript.jscomp.VarCheck.visit(VarCheck.java:207)
at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:730)
at com.google.javascript.jscomp.NodeTraversal.traverseChildren(NodeTraversal.java:802)
at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:726)
at com.google.javascript.jscomp.NodeTraversal.traverseChildren(NodeTraversal.java:802)
at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:726)
at com.google.javascript.jscomp.NodeTraversal.traverseChildren(NodeTraversal.java:802)
at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:726)
at com.google.javascript.jscomp.NodeTraversal.traverseChildren(NodeTraversal.java:802)
at com.google.javascript.jscomp.NodeTraversal.traverseBlockScope(NodeTraversal.java:817)
at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:724)
at com.google.javascript.jscomp.NodeTraversal.traverseFunction(NodeTraversal.java:761)
at com.google.javascript.jscomp.NodeTraversal.handleFunction(NodeTraversal.java:692)
at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:708)
at com.google.javascript.jscomp.NodeTraversal.traverseChildren(NodeTraversal.java:802)
at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:726)
at com.google.javascript.jscomp.NodeTraversal.traverseChildren(NodeTraversal.java:802)
at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:726)
at com.google.javascript.jscomp.NodeTraversal.traverseChildren(NodeTraversal.java:802)
at com.google.javascript.jscomp.NodeTraversal.handleScript(NodeTraversal.java:680)
at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:705)
at com.google.javascript.jscomp.NodeTraversal.traverseChildren(NodeTraversal.java:802)
at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:726)
at com.google.javascript.jscomp.NodeTraversal.traverseRoots(NodeTraversal.java:325)
at com.google.javascript.jscomp.VarCheck.process(VarCheck.java:145)
at com.google.javascript.jscomp.PhaseOptimizer$NamedPass.process(PhaseOptimizer.java:307)
at com.google.javascript.jscomp.PhaseOptimizer.process(PhaseOptimizer.java:233)
at com.google.javascript.jscomp.Compiler.performOptimizations(Compiler.java:2459)
at com.google.javascript.jscomp.Compiler$3.call(Compiler.java:844)
at com.google.javascript.jscomp.Compiler$3.call(Compiler.java:840)
at com.google.javascript.jscomp.CompilerExecutor$2.call(CompilerExecutor.java:93)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.IllegalStateException: Unexpected variable $jscomp
... 35 more
```