fix Type.children() to go up namespace chain

VERSIONS

@@ -55,7 +55,8 @@ ChucK VERSIONS log
     suffice, assuming there are no filename conflicts elsewhere in the 
     import paths)
 ******************************************************
-- (added) member function in Object:
+- (added) member function in Object to get the instantiated type of an
+    object, regardless of the apparent type
     Type Object.typeOfInstance()
         Get the instanced type of this object.
 - (fixed) specific internal UGen connection error now handled without 
@@ -64,6 +65,12 @@ ChucK VERSIONS log
     now are distinguished from windows drive letters (e.g., "A:\")
 - (fixed) Type.of() now reports more specific array type (e.g., 
     `string[]`) instead ofgeneric `@array`
+- (fixed) type system [user] namespace now instantiated correctly at
+    initialization; previously [global] was used until a clearVM was 
+    performed -- this caused incorrect behavior with certain functionality,
+    including a crash in Type.children(); relatedly a long-standing
+    bug was fixed in the type system scope::lookup mechanism that added
+    NULL entries during lookup
 - (fixed) modulo `%` by zero (int or float) now throws an exception; 
     previously this would either produce an incorrect result or cause a 
     crash

src/core/chuck_lang.cpp

@@ -3452,25 +3452,34 @@ CK_DLL_MFUN( type_children )
 
     // instantiate
     Chuck_ArrayInt * ret = new Chuck_ArrayInt( TRUE );
+    // initialize as chuck object
     initialize_object( ret, VM->env()->ckt_array, SHRED, VM );
-
-    // results
-    vector<Chuck_Type *> types;
-    // get types
-    VM->env()->nspc_top()->get_types( types );
-    // clear
+    // clear the vector
     ret->m_vector.clear();
-    // iterate
-    for( t_CKINT i = 0; i < types.size(); i++ )
+
+    // get the current top-most namespace
+    Chuck_Namespace * nspc = VM->env()->nspc_top();
+    // while we have a namespace
+    while( nspc != NULL )
     {
-        // skip me
-        if( equals( types[i], me ) ) continue;
-        // skip if not a subclass of me
-        if( !isa( types[i], me ) ) continue;
-        // copy
-        ret->m_vector.push_back( (t_CKINT)types[i] );
-        // add reference
-        CK_SAFE_ADD_REF( types[i] );
+        // results
+        vector<Chuck_Type *> types;
+        // get types
+        nspc->get_types( types );
+        // iterate
+        for( t_CKINT i = 0; i < types.size(); i++ )
+        {
+            // skip me
+            if( equals( types[i], me ) ) continue;
+            // skip if not a subclass of me
+            if( !isa( types[i], me ) ) continue;
+            // append to vector
+            ret->m_vector.push_back( (t_CKINT)types[i] );
+            // add reference
+            CK_SAFE_ADD_REF( types[i] );
+        }
+        // go up the namespace, e.g., from [user] to [global]
+        nspc = nspc->parent;
     }
 
     // return