BUG/MINOR: vars/compil: fix some warnings

A switch case doesn't have default entry, and the compilator sends
a warning about uninitilized var.

   warning: 'vars' may be used uninitialized in this function [-Wmaybe-uninitialized]
diff --git a/src/vars.c b/src/vars.c
index cf3275c..fe78c46 100644
--- a/src/vars.c
+++ b/src/vars.c
@@ -205,7 +205,8 @@
 	case SCOPE_SESS: vars = &smp->strm->vars_sess;   break;
 	case SCOPE_TXN:  vars = &smp->strm->vars_txn;    break;
 	case SCOPE_REQ:
-	case SCOPE_RES:  vars = &smp->strm->vars_reqres; break;
+	case SCOPE_RES:
+	default:         vars = &smp->strm->vars_reqres; break;
 	}
 	if (vars->scope != var_desc->scope)
 		return 0;
@@ -320,7 +321,8 @@
 	case SCOPE_SESS: vars = &strm->vars_sess;   break;
 	case SCOPE_TXN:  vars = &strm->vars_txn;    break;
 	case SCOPE_REQ:
-	case SCOPE_RES:  vars = &strm->vars_reqres; break;
+	case SCOPE_RES:
+	default:         vars = &strm->vars_reqres; break;
 	}
 	if (vars->scope != scope)
 		return 0;
@@ -395,7 +397,8 @@
 	case SCOPE_SESS: vars = &strm->vars_sess;   break;
 	case SCOPE_TXN:  vars = &strm->vars_txn;    break;
 	case SCOPE_REQ:
-	case SCOPE_RES:  vars = &strm->vars_reqres; break;
+	case SCOPE_RES:
+	default:         vars = &strm->vars_reqres; break;
 	}
 
 	/* Check if the scope is avalaible a this point of processing. */