fix a problem in #load: instead of crashing if we cannot locate the e…

…ntry point of a .rbo file, raise an exception with a message explaining the most common problem cause instead

git-svn-id: http://svn.macosforge.org/repository/ruby/MacRuby/trunk@5197 23306eb0-4c56-4727-a40e-e92c0eb68959

dln.c

@@ -123,7 +123,9 @@ dln_load(const char *file, bool call_init)
 	    (*init_fct)();
 	}
 	else {
-	    assert(__mrep__ != NULL);
+	    if (__mrep__ == NULL) {
+		rb_raise(rb_eLoadError, "Can't load %s: entry point function not located (this can happen when you load twice the same .rbo file with a different case on a case-insensitive filesystem)", file);
+	    }
 	    ((IMP)__mrep__)((id)rb_vm_top_self(), 0);
 	}