Only check int value if set in hasValue

The logic before could result in the method returning true even if the value did not match due to checking an unset (0) int value against a double value that casts to 0.

Resolves micrometer-metricsgh-3535

implementations/micrometer-registry-signalfx/src/test/java/io/micrometer/signalfx/SignalFxMeterRegistryTest.java

@@ -331,7 +331,13 @@ private static Condition<SignalFxProtocolBuffers.DataPoint> gaugePoint(String na
     private static Condition<SignalFxProtocolBuffers.DataPoint> hasValue(double value) {
         return new Condition<>(point -> {
             SignalFxProtocolBuffers.Datum v = point.getValue();
-            return v.getDoubleValue() == value || v.getIntValue() == (int) value;
+            if (v.hasDoubleValue()) {
+                return v.getDoubleValue() == value;
+            }
+            if (v.hasIntValue()) {
+                return v.getIntValue() == (int) value;
+            }
+            return false;
         }, "Has value %s", value);
     }