Fix non-existent response from multires query on empty array

This commit fixes an issue where a multires query on an empty
array will result in a non-existent (empty string) result.

For example `Get("[]", "#(key=value)#").Raw` resulted in an
empty string. But, it should actually result in the empty
array `[]`.

gjson.go

@@ -1406,7 +1406,6 @@ func parseArray(c *parseContext, i int, path string) (int, bool) {
 		}
 		return false
 	}
-
 	for i < len(c.json)+1 {
 		if !rp.arrch {
 			pmatch = partidx == h
@@ -1608,11 +1607,18 @@ func parseArray(c *parseContext, i int, path string) (int, bool) {
 					c.calcd = true
 					return i + 1, true
 				}
-				if len(multires) > 0 && !c.value.Exists() {
+				if !c.value.Exists() {
+					if len(multires) > 0 {
 						c.value = Result{
 							Raw:  string(append(multires, ']')),
 							Type: JSON,
 						}
+					} else if rp.query.all {
+						c.value = Result{
+							Raw:  "[]",
+							Type: JSON,
+						}
+					}
 				}
 				return i + 1, false
 			}

gjson_test.go

@@ -2233,3 +2233,8 @@ func TestFlattenRemoveNonExist(t *testing.T) {
 	raw := Get("[[1],[2,[[],[3]],[4,[5],[],[[[6]]]]]]", `@flatten:{"deep":true}`).Raw
 	assert(t, raw == "[1,2,3,4,5,6]")
 }
+
+func TestPipeEmptyArray(t *testing.T) {
+	raw := Get("[]", `#(hello)#`).Raw
+	assert(t, raw == "[]")
+}