Some misc fixes (#836)

* Fix setup-system breaking in macOS due to unavailable envvar
 - Remove unused docker build-arg from ffmpeg workflow
 - Fix Overview Explorer extending below inspector
 - Fix some left behind formatting problems

* Some more formatting

.github/scripts/setup-system.sh

@@ -316,7 +316,7 @@ elif [ "$SYSNAME" = "Darwin" ]; then
   for _lib in "${_frameworks_dir}/FFMpeg.framework/Libraries/"*; do
     if [ -f "$_lib" ]; then
       # Sign the lib with the local machine certificate (Required for it to work on macOS 13+)
-      if ! codesign -s "$APPLE_SIGNING_IDENTITY" -f "$_lib" 1>/dev/null 2>&1; then
+      if ! codesign -s "${APPLE_SIGNING_IDENTITY:--}" -f "$_lib" 1>/dev/null 2>&1; then
         err "Failed to sign: ${_lib#"$_frameworks_dir"}" \
           'Please open an issue on https://github.com/spacedriveapp/spacedrive/issues'
       fi