Return error if allocation of new element was not possible.

Found by Coverity.

src/interfaces/ecpg/pgtypeslib/numeric.c

@@ -402,14 +402,18 @@ PGTYPESnumeric_to_asc(numeric *num, int dscale)
 	numeric    *numcopy = PGTYPESnumeric_new();
 	char	   *s;
 
-	if (dscale < 0)
-		dscale = num->dscale;
+	if (numcopy == NULL)
+		return NULL;
 
 	if (PGTYPESnumeric_copy(num, numcopy) < 0)
 	{
 		PGTYPESnumeric_free(numcopy);
 		return NULL;
 	}
+
+	if (dscale < 0)
+		dscale = num->dscale;
+
 	/* get_str_from_var may change its argument */
 	s = get_str_from_var(numcopy, dscale);
 	PGTYPESnumeric_free(numcopy);
@@ -1493,6 +1497,9 @@ numericvar_to_double(numeric *var, double *dp)
 	char	   *endptr;
 	numeric    *varcopy = PGTYPESnumeric_new();
 
+	if (varcopy == NULL)
+		return -1;
+
 	if (PGTYPESnumeric_copy(var, varcopy) < 0)
 	{
 		PGTYPESnumeric_free(varcopy);