inst_proposal.rb - handle nil Autoyast proposal list

do not display empty proposal when nil is received
from AutoinstConfig.getProposalList()

src/clients/inst_proposal.rb

@@ -898,9 +898,12 @@ def load_matching_submodules_list
         @submodules_presentation = Builtins.maplist(modules) do |mod|
           Ops.get_string(mod, 0, "")
         end
+
         p = AutoinstConfig.getProposalList
-        @submodules_presentation = Builtins.filter(@submodules_presentation) do |v|
-          Builtins.contains(p, v) || p == []
+
+        if p != nil && p != []
+          # array intersection
+          @submodules_presentation = @submodules_presentation & v
         end
       end