Test invalid chars in expression

Signed-off-by: Michal Čihař <michal@cihar.com>

Author: nijel

src/Expression.php

@@ -84,7 +84,7 @@ public static function factory($value) {
                 return new Expressions\OperatorAnd($value);
         }
 
-        throw new \Exception('Undefined Value ' . $value);
+        throw new \RuntimeException('Undefined Value ' . $value);
     }
 
     abstract public function operate(Stack $stack, $variables=array());

tests/CalculateTest.php

@@ -183,6 +183,7 @@ public function errorEquations()
             array('1 + (1 : 2)'),
             array('(1 + 2'),
             array('1 + 2)'),
+            array('#'),
         );
     }
 }