Empty enum setting in configuration file

In case we have an empty setting in the doxygen configuration file, where an enum value is expected like:
```
OUTPUT_LANGUAGE =
```
we get the warning:
```
warning: argument '(null)' for option OUTPUT_LANGUAGE is not a valid enum value
Using the default: English!
```

The default value should immediately have been used.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/configimpl.l b/src/configimpl.l
index d07e25c..da94484 100644
--- a/src/configimpl.l
+++ b/src/configimpl.l
@@ -234,6 +234,11 @@ void ConfigBool::convertStrToVal()
 
 void ConfigEnum::convertStrToVal()
 {
+  if (m_value.isEmpty())
+  {
+    m_value = m_defValue;
+    return;
+  }
   QCString val = m_value.stripWhiteSpace().lower();
   const char *s=m_valueRange.first();
   while (s)