Issue title: Dotnet run a web project failed with Unhandled expection after isntall .NET Core 3.0 Preview 7
 Issue body: ## Steps to reproduce
1.Install .NET Core 3.0 Preview 6 build 3.0.100-preview7-012621
2.Open Cmd, create a c# ASP.NET Core web project
3.Dotnet run 

## Expected  behavior
Dotnet  run succeeded.

## Actual behavior
Dotnet run failed
![image](https://user-images.githubusercontent.com/38854445/60165775-804fa200-9832-11e9-94e4-97268c7b4f15.png)

Note:
    1.This issue is repro when we create webapi/mvc， also repro on f#
    2. Dotnet restore and dotnet build works fine

## Environment data
`dotnet --info` output:
.NET Core SDK (reflecting any global.json):
 Version:   3.0.100-preview7-012621​
 Commit:    629a4be4f6​
​
Runtime Environment:​
 OS Name:     Mac OS X​
 OS Version:  10.14​
 OS Platform: Darwin​
 RID:         osx.10.14-x64​
 Base Path:   /usr/local/share/dotnet/sdk/3.0.100-preview7-012621/​
​
Host (useful for support):​
  Version: 3.0.0-preview7-27825-10​
  Commit:  2954215e45​
​
.NET Core SDKs installed:​
  3.0.100-preview7-012621 [/usr/local/share/dotnet/sdk]​
​
.NET Core runtimes installed:​
  Microsoft.AspNetCore.App 3.0.0-preview7.19325.3 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]​
  Microsoft.NETCore.App 3.0.0-preview7-27825-10 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]​
​
To install additional .NET Core runtimes or SDKs:​
  https://aka.ms/dotnet-download​
 Comments: 
 Comment 0: This seems more like a asp.net issue.

@anurse can you direct this issue appropriately?
 Comment 1: This issue was moved to aspnet/Extensions#1891
 Comment 2: thanks @anurse 
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