Some more compile time errors, some bug fixes for runtime

scmvm/assembler.scm

@@ -76,7 +76,10 @@
       (when (eq? (car inst) 'push)
         (if (number? (cadr inst))
             (write-word (cadr inst))
-            (write-word (assq-ref labels (cadr inst)))))
+            (let ([address (assq-ref labels (cadr inst))])
+              (if address
+                  (write-word (assq-ref labels (cadr inst)))
+                  (error (format #f "Could not find label ~a" (cadr inst)))))))
       (assembly-pass (cdr seq) labels))]))
 
 (define (assemble instructions port)