Add pre-assert, fix comment

tinyxml2.cpp

@@ -1846,6 +1846,7 @@ void XMLDocument::Print( XMLPrinter* streamer ) const
 
 void XMLDocument::SetError( XMLError error, const char* str1, const char* str2 )
 {
+    TIXMLASSERT( error >= 0 && error < XML_ERROR_COUNT );
     _errorID = error;
     _errorStr1 = str1;
     _errorStr2 = str2;
@@ -1853,7 +1854,7 @@ void XMLDocument::SetError( XMLError error, const char* str1, const char* str2 )
 
 const char* XMLDocument::ErrorName() const
 {
-	TIXMLASSERT(_errorID >= 0 && _errorID < XML_ERROR_COUNT );
+	TIXMLASSERT( _errorID >= 0 && _errorID < XML_ERROR_COUNT );
 	return _errorNames[_errorID];
 }
 

tinyxml2.h

@@ -491,7 +491,7 @@ public:
     }
 };
 
-// WARNING: must match XMLErrorNames[]
+// WARNING: must match XMLDocument::_errorNames[]
 enum XMLError {
     XML_SUCCESS = 0,
     XML_NO_ERROR = 0,