Prevent source line wrapping in rescue layout

Long source lines cause line wrapping in the extracted
source section of the rescue handler page which can make
the line numbers not match up with the source lines.

actionpack/lib/action_dispatch/middleware/templates/rescues/layout.erb

@@ -106,6 +106,7 @@
 
     .line {
       padding-left: 10px;
+      white-space: pre;
     }
 
     .line:hover {