Crash in case of usage of \line without \include

In case thee `line` command is used without previous `\inclide` or `\dontinclude` command doxygen will crash due to a non initialized fd.
We get the message:
warning: No previous '\include' or \dontinclude' command for '\line' present

also a small correcting regarding the warning message is done.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/htmldocvisitor.cpp b/src/htmldocvisitor.cpp
index 37f6bd0..a45e2a7 100644
--- a/src/htmldocvisitor.cpp
+++ b/src/htmldocvisitor.cpp
@@ -790,7 +790,7 @@ void HtmlDocVisitor::visit(DocIncOperator *op)
     popEnabled();
     if (!m_hide) 
     {
-      FileDef *fd;
+      FileDef *fd = NULL;
       if (!op->includeFileName().isEmpty())
       {
         QFileInfo cfi( op->includeFileName() );