Fix nullptr access on media query without type

Fixes #3030

Author: mgreter

src/parser.cpp

@@ -2247,15 +2247,17 @@ namespace Sass {
     if (lex < kwd_not >()) { media_query->is_negated(true); lex < css_comments >(false); }
     else if (lex < kwd_only >()) { media_query->is_restricted(true); lex < css_comments >(false); }
 
-    if (lex < identifier_schema >())  media_query->media_type(parse_identifier_schema());
-    else if (lex < identifier >())    media_query->media_type(parse_interpolated_chunk(lexed));
+    if (lex < identifier_schema >()) media_query->media_type(parse_identifier_schema());
+    else if (lex < identifier >())   media_query->media_type(parse_interpolated_chunk(lexed));
     else                             media_query->append(parse_media_expression());
 
     while (lex_css < kwd_and >()) media_query->append(parse_media_expression());
     if (lex < identifier_schema >()) {
       String_Schema* schema = SASS_MEMORY_NEW(String_Schema, pstate);
-      schema->append(media_query->media_type());
-      schema->append(SASS_MEMORY_NEW(String_Constant, pstate, " "));
+      if (media_query->media_type()) {
+        schema->append(media_query->media_type());
+        schema->append(SASS_MEMORY_NEW(String_Constant, pstate, " "));
+      }
       schema->append(parse_identifier_schema());
       media_query->media_type(schema);
     }