minor readme fixes

tinyxml2.cpp

@@ -114,9 +114,6 @@ distribution.
 	#define TIXML_VSNPRINTF	vsnprintf
 	static inline int TIXML_VSCPRINTF( const char* format, va_list va )
 	{
-	    if (!format) {
-	        return 0;
-	    }
 		int len = vsnprintf( 0, 0, format, va );
 		TIXMLASSERT( len >= 0 );
 		return len;
@@ -2347,11 +2344,9 @@ static FILE* callfopen( const char* filepath, const char* mode )
     return fp;
 }
 
-void XMLDocument::DeleteNode( XMLNode* node )	{   
-    if(node == 0) {
-        return; // check for null pointer
-    }
-    TIXMLASSERT(node->_document == this);
+void XMLDocument::DeleteNode( XMLNode* node )	{
+    TIXMLASSERT( node );
+    TIXMLASSERT(node->_document == this );
     if (node->_parent) {
         node->_parent->DeleteChild( node );
     }

xmltest.cpp

@@ -2025,13 +2025,7 @@ int main( int argc, const char ** argv )
 		XMLTest("Parse nested elements with pedantic whitespace", false, doc.Error());
 		XMLTest("Pedantic whitespace", true, 0 == doc.RootElement()->FirstChildElement()->GetText());
 	}
-	//Check the robustness of the DeleteNode function in handling null pointers.
-	{
-		XMLDocument doc;
-		doc.DeleteNode(nullptr);
-		XMLTest("DeleteNode with null pointer", true, doc.Error() == XML_SUCCESS);
-	}
-		
+
 	// Check sample xml can be parsed with pedantic mode
 	{
 		XMLDocument doc(true, PEDANTIC_WHITESPACE);