[vi-mode] GotoFirstNonBlankOfLine crashes PSRL when buffer is empty #2050

PS version: 7.2.0-daily.20201215
PSReadline version: 2.1.0
os: 10.0.18362.1130 (WinBuild.160101.0800)
PS file version: 7.2.0.0
HostName: ConsoleHost (Windows Terminal)
BufferWidth: 120
BufferHeight: 30

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System.IndexOutOfRangeException: Index was outside the bounds of the array.
   at System.Text.StringBuilder.get_Chars(Int32 index)
   at Microsoft.PowerShell.PSConsoleReadLine.IsVisibleBlank(Int32 newCurrent)
   at Microsoft.PowerShell.PSConsoleReadLine.GetFirstNonBlankOfLogicalLinePos(Int32 current)
   at Microsoft.PowerShell.PSConsoleReadLine.GotoFirstNonBlankOfLine(Nullable`1 key, Object arg)
   at Microsoft.PowerShell.PSConsoleReadLine.ProcessOneKey(PSKeyInfo key, Dictionary`2 dispatchTable, Boolean ignoreIfNoAction, Object arg)
   at Microsoft.PowerShell.PSConsoleReadLine.InputLoop()
   at Microsoft.PowerShell.PSConsoleReadLine.ReadLine(Runspace runspace, EngineIntrinsics engineIntrinsics, CancellationToken cancellationToken)