Fix `enable_debug_info?` in `mrbgems/mruby-proc-ext/test/proc.rb`

mrbgems/mruby-proc-ext/test/proc.rb

@@ -7,9 +7,10 @@ def enable_debug_info?
     raise
   rescue => e
     @enable_debug_info = !e.backtrace.empty?
-    if(@enable_debug_info && e.backtrace[0].include?("(unknown)"))
+    if @enable_debug_info && e.backtrace[0].include?("(unknown)")
       @enable_debug_info = false
     end
+    return @enable_debug_info
   end
 end