raster-interpret.c: Verify base for strtol()

Input for `atoi()` can be bad number for argument `base` in `strtol()`,
causing returning an incorrect pointer address and later segfault.

Break out from function if the base is incorrect.

Fixes OpenPrinting#1188

Author: zdohnal

cups/raster-interpret.c

@@ -1306,10 +1306,10 @@ scan_ps(_cups_ps_stack_t *st,		/* I  - Stack */
 	  base = atoi(start);
 
 	 /*
-	  * strtol() takes 0 or 2 to 32 as base...
+	  * Postscript language reference manual dictates numbers from 2 to 36 as base...
 	  */
 
-	  if (base != 0 && (base < 2 || base > 32))
+	  if (base < 2 || base > 36)
 	    return (NULL);
 
 	  obj.value.number = strtol(cur + 1, &cur, base);