TW-1692: 42//' segfaults

- Thanks to Daniel Shahaf.

ChangeLog

@@ -152,6 +152,7 @@
 - TW-1687 task add due:som appears to be interpreted as 'someday' (thanks to
           Alan Young).
 - TW-1688 task fails to import (thanks to Rainer Müller).
+- TW-1692 42//' segfaults (thanks to Daniel Shahaf).
 - Prevent potential task duplication during import for non-pending tasks.
 - Show the active context in "context list", if any is active.
 - Fix "task edit" dropping annotation text after newlines.

src/DOM.cpp

@@ -65,6 +65,10 @@ DOM::~DOM ()
 //
 bool DOM::get (const std::string& name, Variant& value)
 {
+  // Special case, blank refs cause problems.
+  if (name == "")
+    return false;
+
   int len = name.length ();
   Nibbler n (name);
 
@@ -196,6 +200,10 @@ bool DOM::get (const std::string& name, Variant& value)
 // as special cases.
 bool DOM::get (const std::string& name, const Task& task, Variant& value)
 {
+  // Special case, blank refs cause problems.
+  if (name == "")
+    return false;
+
   // Quickly deal with the most common cases.
   if (task.size () && name == "id")
   {