erb.rb: Prevent potential unexpected rescue

of LoadError in some method calls, not from `require "strscan"`.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58822 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/erb.rb

@@ -501,6 +501,8 @@ class ERB
 
     begin
       require 'strscan'
+    rescue LoadError
+    else
       class SimpleScanner < Scanner # :nodoc:
         def scan
           stag_reg = /(.*?)(#{stags.join('|')}|\z)/m
@@ -540,8 +542,6 @@ class ERB
         end
       end
       Scanner.regist_scanner(ExplicitScanner, '-', false)
-
-    rescue LoadError
     end
 
     class Buffer # :nodoc: