Remove hasTargets member variable and fix docs warnings (#283)

hasTargets is redundant because the same information can be obtained by
checking the size of the targets array.

photon-lib/src/main/native/include/photonlib/PhotonCamera.h

@@ -17,12 +17,13 @@
 
 #pragma once
 
+#include <memory>
+#include <string>
+
 #include <networktables/NetworkTable.h>
 #include <networktables/NetworkTableEntry.h>
 #include <networktables/NetworkTableInstance.h>
-
-#include <memory>
-#include <string>
+#include <wpi/deprecated.h>
 
 #include "photonlib/PhotonPipelineResult.h"
 
@@ -118,9 +119,11 @@ class PhotonCamera {
    * This method is deprecated; {@link PhotonPipelineResult#hasTargets()} should
    * be used instead.
    * @deprecated This method should be replaced with {@link
-   * PhotonPipelineResult#hasTargets()}
+   * PhotonPipelineResult#HasTargets()}
    * @return Whether the latest target result has targets.
    */
+  WPI_DEPRECATED(
+      "This method should be replaced with PhotonPipelineResult::HasTargets()")
   bool HasTargets() const { return GetLatestResult().HasTargets(); }
 
  private:

photon-lib/src/main/native/include/photonlib/PhotonPipelineResult.h

@@ -57,12 +57,12 @@ class PhotonPipelineResult {
     if (!HasTargets() && !HAS_WARNED) {
       ::frc::DriverStation::ReportError(
           "This PhotonPipelineResult object has no targets associated with it! "
-          "Please check hasTargets() before calling this method. For more "
+          "Please check HasTargets() before calling this method. For more "
           "information, please review the PhotonLib documentation at "
           "http://docs.photonvision.org");
       HAS_WARNED = true;
     }
-    return hasTargets ? targets[0] : PhotonTrackedTarget();
+    return HasTargets() ? targets[0] : PhotonTrackedTarget();
   }
 
   /**
@@ -75,7 +75,7 @@ class PhotonPipelineResult {
    * Returns whether the pipeline has targets.
    * @return Whether the pipeline has targets.
    */
-  bool HasTargets() const { return hasTargets; }
+  bool HasTargets() const { return targets.size() > 0; }
 
   /**
    * Returns a reference to the vector of targets.
@@ -93,7 +93,6 @@ class PhotonPipelineResult {
 
  private:
   units::second_t latency = 0_s;
-  bool hasTargets = false;
   wpi::SmallVector<PhotonTrackedTarget, 10> targets;
   inline static bool HAS_WARNED = false;
 };