fix <C-n> issue with mapping_wrapper()

ctrl mapping is not well handled with mapping_wrapper() function,
culprit may be the <C- interpreted somewhere...

Workaround is to directly map the command when no section regex is
provided to mg_set_mapping function.

error message:
E114: Missing quote: "
E116: Invalid arguments for function <SNR>134_mapping_wrapper

autoload/magit/mapping.vim

@@ -73,14 +73,20 @@ endfunction
 " param[in] function the function to call (rhs)
 " param[in] ... : optional, section, the regex of the section(s)
 function! s:mg_set_mapping(mode, mapping, function, ...)
+	if ( a:0 == 1 )
 		execute a:mode . "noremap <buffer><silent><nowait> "
 					\ . a:mapping .
 					\ " :call <SID>mapping_wrapper(\"" .
 					\ a:mapping . "\", \"" .
 					\ a:function . "\"" .
-				\ ( ( a:0 == 1 ) ?
-				\ ", \'" . a:1 . "\'" : '' )
-				\ . ")<cr>"
+					\ ", \'" . a:1 . "\'" .
+					\ ")<cr>"
+	else
+		execute a:mode . "noremap <buffer><silent><nowait> "
+					\ . a:mapping .
+					\ " :call  " .
+					\ a:function . "<cr>"
+	endif
 endfunction
 
 function! magit#mapping#set_default()