Do not try to access non-existen string index.

tests/base32_test.aer

@@ -55,8 +55,10 @@ class Base32 {
 			if(!in_array($input[$i], Base32::$map))
 				return '';
 			for(int $j = 0; $j < 8; $j++) {
-				if(array_key_exists($input[$i + $j], Base32::$flippedMap)) {
-					$x += str_pad(base_convert(Base32::$flippedMap[$input[$i + $j]], 10, 2), 5, '0', STR_PAD_LEFT);
+				if($i + $j < strlen($input)) {
+					if(array_key_exists($input[$i + $j], Base32::$flippedMap)) {
+						$x += str_pad(base_convert(Base32::$flippedMap[$input[$i + $j]], 10, 2), 5, '0', STR_PAD_LEFT);
+					}
 				}
 			}
 			string[] $eightBits = str_split($x, 8);