Remove some unnecessary function_exists() checks and some minor improvements
diff --git a/system/libraries/Unit_test.php b/system/libraries/Unit_test.php
index a87cf7e..70ad8dc 100644
--- a/system/libraries/Unit_test.php
+++ b/system/libraries/Unit_test.php
@@ -124,7 +124,7 @@
 
 		$this->results[] = $report;
 
-		return($this->report($this->result($report)));
+		return $this->report($this->result($report));
 	}
 
 	// --------------------------------------------------------------------
@@ -289,15 +289,11 @@
 	 */
 	protected function _backtrace()
 	{
-		if (function_exists('debug_backtrace'))
-		{
-			$back = debug_backtrace();
-			return array(
-					'file' => (isset($back[1]['file']) ? $back[1]['file'] : ''),
-					'line' => (isset($back[1]['line']) ? $back[1]['line'] : '')
-				);
-		}
-		return array('file' => 'Unknown', 'line' => 'Unknown');
+		$back = debug_backtrace();
+		return array(
+				'file' => (isset($back[1]['file']) ? $back[1]['file'] : ''),
+				'line' => (isset($back[1]['line']) ? $back[1]['line'] : '')
+			);
 	}
 
 	// --------------------------------------------------------------------