[grubcfg] Avoid crashes in tests

- remove "bogus" key when it's not needed
- check for existence of "branding" key in GS before
  subscripting it (this happens in tests, where no
  GS contents are loaded, but not in regular use,
  where startup loads the branding data into GS)

src/modules/grubcfg/main.py

@@ -281,7 +281,10 @@ def run():
     partitions = libcalamares.globalstorage.value("partitions")
     root_mount_point = libcalamares.globalstorage.value("rootMountPoint")
     branding = libcalamares.globalstorage.value("branding")
-    distributor = branding["bootloaderEntryName"]
+    if branding is None:
+        distributor = None
+    else:
+        distributor = branding["bootloaderEntryName"]
 
     if libcalamares.globalstorage.value("bootLoader") is None and fw_type != "efi":
         return None

src/modules/grubcfg/tests/1.global

@@ -1,4 +1,5 @@
 # SPDX-FileCopyrightText: no
 # SPDX-License-Identifier: CC0-1.0
 ---
-bogus: true
+branding:
+  bootloaderEntryName: generic

src/modules/grubcfg/tests/2.global

@@ -1,7 +1,6 @@
 # SPDX-FileCopyrightText: no
 # SPDX-License-Identifier: CC0-1.0
 ---
-bogus: true
 firmwareType: bios
 bootLoader: grub
 rootMountPoint: /tmp/calamares/grubcfg-test-2

src/modules/grubcfg/tests/3.global

@@ -1,7 +1,6 @@
 # SPDX-FileCopyrightText: no
 # SPDX-License-Identifier: CC0-1.0
 ---
-bogus: true
 firmwareType: bios
 bootLoader: grub
 rootMountPoint: /tmp/calamares/grubcfg-test-3

src/modules/grubcfg/tests/4.global

@@ -1,7 +1,6 @@
 # SPDX-FileCopyrightText: no
 # SPDX-License-Identifier: CC0-1.0
 ---
-bogus: true
 firmwareType: bios
 bootLoader: grub
 rootMountPoint: /tmp/calamares/grubcfg-test-4