Fix a copy-pasta error.

src/vfp.c

@@ -912,7 +912,7 @@ vfp_encrypt_pull(struct vfp_ctx *ctx, struct vfp_entry *ent, void *ptr,
 			}
 		}
 		else if (vp != VFP_END)
-			ERR_DEC(ctx, "message truncated");
+			ERR_ENC(ctx, "message truncated");
 	}
 
 	*lenp = outputLen(stream, p);