Small update to documentation (#218)

I corrected a sentence by adding an 'if' in the middle.

pollen/scribblings/formats.scrbl

@@ -163,7 +163,7 @@ Scribble files are recognized by the project server and can be compiled and prev
 
 Files with the null extension are simply rendered as a copy of the file without the extension, so @filepath{index.html.p} becomes @filepath{index.html}. 
 
-This can be useful you're managing your project with Git. Most likely you'll want to ignore @filepath{*.html} and other file types that are frequently regenerated by the project server. But if you have isolated static files — for instance, a @filepath{index.html} that doesn't have source associated with it — they'll be ignored too. You can cure this problem by appending the null extension to these static files, so they'll be tracked in your source system without actually being source files. 
+This can be useful if you're managing your project with Git. Most likely you'll want to ignore @filepath{*.html} and other file types that are frequently regenerated by the project server. But if you have isolated static files — for instance, a @filepath{index.html} that doesn't have source associated with it — they'll be ignored too. You can cure this problem by appending the null extension to these static files, so they'll be tracked in your source system without actually being source files. 
 
 The null extension is also useful for templates — @filepath{template.html} and @filepath{template.html.p} will work the same way.