Fix Error Message display in new Values and Types chapter (#537) (#538)

Original PR: #537

Author: JPryce-Aklundh

modules/ROOT/pages/values-and-types/casting-data.adoc

@@ -98,7 +98,7 @@ WITH date({
 RETURN toFloat(d)
 ----
 
-.
+.Error message
 [source, error]
 ----
 Type mismatch: expected Float, Integer, Number or String but was Date (line 4, column 16 (offset: 66))