Golang x/tools/gopls: template.SemanticTokens: panic in template.(*Parsed).RuneCount

#!stacks
"goPanicIndex" && "template.(*Parsed).RuneCount" && 
"template.SemanticTokens"

Issue created by stacks.

This stack -mHbOA was reported by telemetry:

• crash/crash
• runtime.gopanic:+69,+0x167
• runtime.goPanicIndex:+2,+0x73
• golang.org/x/tools/gopls/internal/template.(*Parsed).RuneCount:+4,+0x16e
• golang.org/x/tools/gopls/internal/template.SemanticTokens:+33,+0x75b
• golang.org/x/tools/gopls/internal/server.(*server).semanticTokens:+13,+0x291
• golang.org/x/tools/gopls/internal/server.(*server).SemanticTokensFull:+1,+0x29
• golang.org/x/tools/gopls/internal/protocol.serverDispatch:+511,+0x6679
• golang.org/x/tools/gopls/internal/lsprpc.(*streamServer).ServeStream.ServerHandler.func4:+5,+0x84
• golang.org/x/tools/gopls/internal/lsprpc.(*streamServer).ServeStream.handshaker.func5:+52,+0x908
• golang.org/x/tools/gopls/internal/protocol.Handlers.MustReplyHandler.func1:+2,+0xc5
• golang.org/x/tools/gopls/internal/protocol.Handlers.AsyncHandler.func2.2:+3,+0x95
• runtime.goexit:+0,+0x0

golang.org/x/tools/gopls@v0.19.1 go1.24.2 linux/amd64 other,vscode (2)