Fix ImagickBackend and i18n Textcollector Task (#39)

Prevents PHP Fatal error: Class 'ImagickBackend' not found when Imagick is not installed.

code/FPImagickBackend.php

@@ -1,18 +1,20 @@
 <?php
-class FPImagickBackend extends ImagickBackend {
-    /**
-     * Crop's part of image.
-     * @param top y position of left upper corner of crop rectangle
-     * @param left x position of left upper corner of crop rectangle
-     * @param width rectangle width
-     * @param height rectangle height
-     * @return ImagickBackend
-     */
-    public function crop($top, $left, $width, $height) {
-        $new = clone $this;
-        $new->cropImage($width, $height, $left, $top);
-
-        return $new;
+if(class_exists('Imagick')) {
+    class FPImagickBackend extends ImagickBackend {
+        /**
+         * Crop's part of image.
+         * @param top y position of left upper corner of crop rectangle
+         * @param left x position of left upper corner of crop rectangle
+         * @param width rectangle width
+         * @param height rectangle height
+         * @return ImagickBackend
+         */
+        public function crop($top, $left, $width, $height) {
+            $new = clone $this;
+            $new->cropImage($width, $height, $left, $top);
+
+            return $new;
+        }
     }
 }
-?>
+?>