Closed Unassigned: forall statement in inductive predicate causes crash [169]

Dafny crashes on the following input:

```
predicate R(x: int)

inductive lemma P(x: int)
{
forall x | R(x)
{
}
}
```

I'm including the stack trace from the crash below.

Rustan


```
> dafny Demo.dfy
Dafny program verifier version 1.9.7.30401, Copyright (c) 2003-2016, Microsoft.

Unhandled Exception: System.Diagnostics.Contracts.__ContractsRuntime+ContractException: Precondition failed: WasResolved()
at System.Diagnostics.Contracts.__ContractsRuntime.TriggerFailure(ContractFailureKind kind, String msg, String userMessage, String conditionTxt, Exception inner) in c:\dafny\Source\Dafny\SccGraph.cs:line 0
at System.Diagnostics.Contracts.__ContractsRuntime.ReportFailure(ContractFailureKind kind, String msg, String conditionTxt, Exception inner) in c:\dafny\Source\Dafny\SccGraph.cs:line 0
at System.Diagnostics.Contracts.__ContractsRuntime.Requires(Boolean condition, String msg, String conditionTxt) in c:\dafny\Source\Dafny\SccGraph.cs:line 0
at Microsoft.Dafny.Expression.get_Resolved() in c:\dafny\Source\Dafny\DafnyAst.cs:line 5489
at Microsoft.Dafny.FixpointLemmaBodyCloner.CloneExpr(Expression expr) in c:\dafny\Source\Dafny\Cloner.cs:line 878
at Microsoft.Dafny.Cloner.CloneExpr(Expression expr) in c:\dafny\Source\Dafny\Cloner.cs:line 388
at Microsoft.Dafny.FixpointLemmaBodyCloner.CloneExpr(Expression expr) in c:\dafny\Source\Dafny\Cloner.cs:line 902
at System.Collections.Generic.List`1.ConvertAll[TOutput](Converter`2 converter)
at Microsoft.Dafny.Cloner.CloneStmt(Statement stmt) in c:\dafny\Source\Dafny\Cloner.cs:line 567
at System.Collections.Generic.List`1.ConvertAll[TOutput](Converter`2 converter)
at Microsoft.Dafny.Cloner.CloneBlockStmt(BlockStmt stmt) in c:\dafny\Source\Dafny\Cloner.cs:line 502
at Microsoft.Dafny.Resolver.ResolveTopLevelDecls_Core(List`1 declarations, Graph`1 datatypeDependencies, Graph`1 codatatypeDependencies) in c:\dafny\Source\Dafny\Resolver.cs:line 1782
at Microsoft.Dafny.Resolver.ResolveModuleDefinition(ModuleDefinition m, ModuleSignature sig) in c:\dafny\Source\Dafny\Resolver.cs:line 729
at Microsoft.Dafny.Resolver.ResolveProgram(Program prog) in c:\dafny\Source\Dafny\Resolver.cs:line 344
at Microsoft.Dafny.Main.ParseCheck(IList`1 fileNames, String programName, ErrorReporter reporter, Program& program) in c:\dafny\Source\Dafny\DafnyMain.cs:line 70
at Microsoft.Dafny.DafnyDriver.ProcessFiles(IList`1 dafnyFileNames, ReadOnlyCollection`1 otherFileNames, ErrorReporter reporter, Boolean lookForSnapshots, String programId) in c:\dafny\Source\DafnyDriver\DafnyDriver.cs:line 174
at Microsoft.Dafny.DafnyDriver.ThreadMain(String[] args) in c:\dafny\Source\DafnyDriver\DafnyDriver.cs:line 106
at Microsoft.Dafny.DafnyDriver.<>c__DisplayClass1.<Main>b__0() in c:\dafny\Source\DafnyDriver\DafnyDriver.cs:line 34
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()
```