ArgumentException: Path is empty error is thrown on cancelling pCache file window in Point Cache Bake Tool.

Steps to repro:
1. Create a new project.
2. Windows > Package Manager > Visual Effects Graph > Install.
3. Windows > Visual Effects > Utilities > Point Cache Bake Tool.
4. Click on Mesh Asset selector button > Select Cube.
5. Press Save to pCache file button > Cancel.

Actual Result:
ArgumentException error is thrown in the console.

Expected Result:
No Error in the console.

Reproducible in:
2020.1.0a1, 2019.3.0b1, 2019.3.0a10.

NOTE:
Visual Effects is introduced in 2019.3.0a10.

Environment:
Windows & Mac 10.14.

Stack trace:
ArgumentException: Path is empty
System.IO.FileStream..ctor (System.String path, System.IO.FileMode mode, System.IO.FileAccess access, System.IO.FileShare share, System.Int32 bufferSize, System.Boolean anonymous, System.IO.FileOptions options) (at <ad04dee02e7e4a85a1299c7ee81c79f6>:0)
System.IO.FileStream..ctor (System.String path, System.IO.FileMode mode, System.IO.FileAccess access, System.IO.FileShare share, System.Int32 bufferSize) (at <ad04dee02e7e4a85a1299c7ee81c79f6>:0)
(wrapper remoting-invoke-with-check) System.IO.FileStream..ctor(string,System.IO.FileMode,System.IO.FileAccess,System.IO.FileShare,int)
System.IO.File.Create (System.String path, System.Int32 bufferSize) (at <ad04dee02e7e4a85a1299c7ee81c79f6>:0)
System.IO.File.Create (System.String path) (at <ad04dee02e7e4a85a1299c7ee81c79f6>:0)
UnityEditor.Experimental.VFX.Utility.PCache.SaveToFile (System.String filename, UnityEditor.Experimental.VFX.Utility.PCache+Format format) (at library/packagecache/com.unity.visualeffectgraph@7.0.1/editor/utilities/pcache/pcache.cs:273)
UnityEditor.Experimental.VFX.Utility.PointCacheBakeTool.OnGUI_Mesh () (at library/packagecache/com.unity.visualeffectgraph@7.0.1/editor/utilities/pcache/baketool/pointcachebaketool.mesh.cs:67)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)