fix incorrect attribute being checked for side info

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: cmfrec
 Type: Package
 Title: Collective Matrix Factorization for Recommender Systems
-Version: 3.5.1-2
+Version: 3.5.1-3
 Authors@R: c(
   person(given="David", family="Cortes", role=c("aut", "cre", "cph"),
          email="[email protected]"),

R/factors_single.R

@@ -92,7 +92,7 @@ process.data.factors.single <- function(model, obj,
     exact        <-  check.bool(exact)
     if (!is.null(U_bin) && !NCOL(obj$matrices$Cb))
         stop("Model was not fit to binary side information.")
-    if ((!is.null(U) || !is.null(U_col) || !is.null(U_val)) && !NCOL(obj$C))
+    if ((!is.null(U) || !is.null(U_col) || !is.null(U_val)) && !NCOL(obj$matrices$C))
         stop("Model was not fit to 'U' data.")
     if (is.null(X_col) != is.null(X_val))
         stop("'X_col' and 'X_val' must be passed in conjunction.")