x/tools/gopls: CodeActions: nil panic in refactorRewriteEliminateDotImport

[adonovan]

#!stacks
"sigpanic" && "types.(*PkgName).Imported" && "refactorRewriteEliminateDotImport:+17"

Issue created by stacks.

This stack LT-h9Q was reported by telemetry:

• crash/crash
• runtime.gopanic:+69,+0x167
• runtime.panicmem:=262,+0x358
• runtime.sigpanic:+19,+0x328
• go/types.(*PkgName).Imported:=258,+0x112
• golang.org/x/tools/gopls/internal/golang.refactorRewriteEliminateDotImport:+17,+0xc0
• golang.org/x/tools/gopls/internal/golang.CodeActions:+64,+0x624
• golang.org/x/tools/gopls/internal/server.(*server).CodeAction:+154,+0x5a8
• golang.org/x/tools/gopls/internal/protocol.serverDispatch:+160,+0x239c
• 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 go1.24.4 linux/amd64 vscode (1)