(fix) add a cast to nsobject in order to avoid a build error in objective-c… (#379)

* add a cast to nsobject in order to avoid a build error in objective-c. Swift works fine. :/

* update travis yaml to user testapp master.  add comments

Author: thomaszurkan-optimizely

.travis.yml

@@ -33,6 +33,7 @@ jobs:
       env:
         - SDK=objective-c
         - BUILD_NUMBER=$TRAVIS_BUILD_NUMBER
+        - TESTAPP_TAG=master
       cache: false
       before_install: skip
       install:

OptimizelySDKShared/OptimizelySDKShared/OPTLYManagerBase.m

@@ -86,8 +86,11 @@ - (void)cleanUserProfileService:(NSArray<OPTLYExperiment *><OPTLYExperiment> *)e
 //#pragma clang diagnostic push
 //#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
                 @try {
-                    IMP imp = [self.userProfileService.class instanceMethodForSelector:selector];
+                    // cast to NSObject.  If the user profile service is not the default service, then an exception will be thrown when trying to access this selector.
+                    IMP imp = [((NSObject *)(self.userProfileService)).class instanceMethodForSelector:selector];
+                    // cast the function
                     void (*func)(id, SEL, NSArray *) = (void *)imp;
+                    // call it.
                     func(self.userProfileService, selector, ids);
                 }
                 @catch(NSException *e) {