added checks to ensure a mode it properly set and supported by the format

git-svn-id: file:///home/svn/framework3/trunk@12860 4d416f70-5f16-0410-b530-b9f4589650da

msfbinscan

@@ -126,7 +126,7 @@ rescue OptionParser::InvalidOption
 	exit(1)
 end
 
-if not mode
+if not mode or mode.nil?
 	puts "A mode must be selected"
 	exit(1)
 end
@@ -198,6 +198,11 @@ files.each do |file|
 			pe.image_base = param['imagebase'];
 		end
 
+		if not worker
+			$stderr.puts("A mode could not be set for this file.")
+			next
+		end
+
 		o = worker.new(pe)
 		o.scan(param)