gps: revamp validSentence() to avoid heap allocation for errors. This error can occur too frequently to allow for such allocations

Signed-off-by: deadprogram <ron@hybridgroup.com>

gps/gpsparser_test.go

@@ -8,13 +8,13 @@ import (
 )
 
 func TestParseUnknownSentence(t *testing.T) {
-	c := qt.New(t)
-
 	p := NewParser()
 
 	val := "$GPGSV,3,1,09,07,14,317,22,08,31,284,25,10,32,133,39,16,85,232,29*7F"
 	_, err := p.Parse(val)
-	c.Assert(err.Error(), qt.Contains, "unsupported NMEA sentence type")
+	if err == nil {
+		t.Error("should have unknown sentence err")
+	}
 }
 
 func TestParseGGA(t *testing.T) {