diff -up firefox-75.0/intl/locale/LocaleService.cpp.locale-debug firefox-75.0/intl/locale/LocaleService.cpp
--- firefox-75.0/intl/locale/LocaleService.cpp.locale-debug	2020-04-06 22:42:20.196799809 +0200
+++ firefox-75.0/intl/locale/LocaleService.cpp	2020-04-06 22:43:02.522530317 +0200
@@ -372,8 +372,6 @@ LocaleService::GetDefaultLocale(nsACStri
     // just use our hard-coded default below.
     GetGREFileContents("update.locale", &locale);
     locale.Trim(" \t\n\r");
-    // This should never be empty.
-    MOZ_ASSERT(!locale.IsEmpty());
     if (CanonicalizeLanguageId(locale)) {
       mDefaultLocale.Assign(locale);
     }