feat: ✨ add deadlock detection to find_next

lib/comfpile/core.rb

@@ -106,6 +106,8 @@ module Comfpile
         end
 
         def processing_stack_find_next()
+            return nil if @processing_stack.empty?
+
             i = 0
             @processing_stack.reverse_each do |a|
                 i += 1
@@ -115,6 +117,9 @@ module Comfpile
                 end
             end
 
+            # TODO: Fix up later-on for parallel runner capabilities
+            raise "Deadlock found, no item was willing to run!"
+
             nil
         end