Merge pull request #7 from lbryio/guard_null_mod

Allow null query mods for dynamic queries

queries/qm/query_mods.go

@@ -8,9 +8,11 @@ type QueryMod func(q *queries.Query)
 // Apply the query mods to the Query object
 func Apply(q *queries.Query, mods ...QueryMod) {
 	for _, mod := range mods {
+		if mod != nil {
 			mod(q)
 		}
 	}
+}
 
 // SQL allows you to execute a plain SQL statement
 func SQL(sql string, args ...interface{}) QueryMod {
@@ -129,7 +131,6 @@ func ForceIndex( index string) QueryMod {
 	}
 }
 
-
 // Limit the number of returned rows
 func Limit(limit int) QueryMod {
 	return func(q *queries.Query) {