Fix filter errors

Prevent error messages from being output to stderr.
Return illegal token when a quoted string is invalid and
capture the error.

Signed-off-by: Derek McGowan <derek@mcgstyle.net>

filters/filter_test.go

@@ -272,6 +272,16 @@ func TestFilters(t *testing.T) {
 			input:     "image~=,id?=?fbaq",
 			errString: `filters: parse error: [image~= >|,|< id?=?fbaq]: expected value or quoted`,
 		},
+		{
+			name:      "FieldQuotedLiteralNotTerminated",
+			input:     "labels.ns/key==value",
+			errString: `filters: parse error: [labels.ns >|/|< key==value]: quoted literal not terminated`,
+		},
+		{
+			name:      "ValueQuotedLiteralNotTerminated",
+			input:     "labels.key==/value",
+			errString: `filters: parse error: [labels.key== >|/|< value]: quoted literal not terminated`,
+		},
 	} {
 		t.Run(testcase.name, func(t *testing.T) {
 			filter, err := Parse(testcase.input)