fixed erroneous error handling in Casper.capture()

@@ -143,6 +143,7 @@
          */
         capture: function(targetFile, clipRect) {
             var previousClipRect;
+            targetFile = require('fs').absolute(targetFile);
             if (clipRect) {
                 if (!isType(clipRect, "object")) {
                     throw new Error("clipRect must be an Object instance.");
@@ -153,10 +154,8 @@
             } else {
                 this.log('Capturing page to ' + targetFile, "debug");
             }
-            try {
-                this.page.render(targetFile);
-            } catch (e) {
-                this.log('Failed to capture screenshot as ' + targetFile + ': ' + e, "error");
+            if (!this.page.render(targetFile)) {
+                this.log('Failed to save screenshot to ' + targetFile + '; please check permissions', "error");
             }
             if (previousClipRect) {
                 this.page.clipRect = previousClipRect;