review some possible nil error panics (#20518)

app/plugin_api_tests/test_set_profile_image_plugin/main.go

@@ -58,7 +58,7 @@ func (p *MyPlugin) MessageWillBePosted(_ *plugin.Context, _ *model.Post) (*model
 	byteReader := bytes.NewReader(imageProfile)
 	img2, _, err2 := image.Decode(byteReader)
 	if err2 != nil {
-		return nil, err.Error()
+		return nil, err2.Error()
 	}
 	if img2.At(2, 3) != colorful {
 		return nil, fmt.Sprintf("color mismatch %v != %v", img2.At(2, 3), colorful)

app/plugin_install.go

@@ -46,7 +46,6 @@ import (
 	"path/filepath"
 
 	"github.com/blang/semver"
-	"github.com/pkg/errors"
 
 	"github.com/mattermost/mattermost-server/v6/model"
 	"github.com/mattermost/mattermost-server/v6/shared/filestore"
@@ -199,8 +198,7 @@ func (ch *Channels) InstallMarketplacePlugin(request *model.InstallMarketplacePl
 	if prepackagedPlugin != nil {
 		fileReader, err := os.Open(prepackagedPlugin.Path)
 		if err != nil {
-			err = errors.Wrapf(err, "failed to open prepackaged plugin %s", prepackagedPlugin.Path)
-			return nil, model.NewAppError("InstallMarketplacePlugin", "app.plugin.install_marketplace_plugin.app_error", nil, err.Error(), http.StatusInternalServerError)
+			return nil, model.NewAppError("InstallMarketplacePlugin", "app.plugin.install_marketplace_plugin.app_error", nil, fmt.Sprintf("failed to open prepackaged plugin %s: %s", prepackagedPlugin.Path, err.Error()), http.StatusInternalServerError)
 		}
 		defer fileReader.Close()
 

app/user.go

@@ -1658,10 +1658,14 @@ func (a *App) SendEmailVerification(user *model.User, newEmail, redirect string)
 	}
 
 	if _, err := a.GetStatus(user.Id); err != nil {
+		if err.StatusCode != http.StatusNotFound {
+			return err
+		}
 		eErr := a.Srv().EmailService.SendVerifyEmail(newEmail, user.Locale, a.GetSiteURL(), token.Token, redirect)
 		if eErr != nil {
 			return model.NewAppError("SendVerifyEmail", "api.user.send_verify_email_and_forget.failed.error", nil, eErr.Error(), http.StatusInternalServerError)
 		}
+
 		return nil
 	}
 
@@ -2310,7 +2314,7 @@ func (a *App) ConvertBotToUser(bot *model.Bot, userPatch *model.UserPatch, sysad
 
 	appErr := a.Srv().Store.Bot().PermanentDelete(bot.UserId)
 	if appErr != nil {
-		return nil, model.NewAppError("ConvertBotToUser", "app.user.convert_bot_to_user.app_error", nil, err.Error(), http.StatusInternalServerError)
+		return nil, model.NewAppError("ConvertBotToUser", "app.user.convert_bot_to_user.app_error", nil, appErr.Error(), http.StatusInternalServerError)
 	}
 
 	return user, nil