fix crash in test with Swift 3.1

I'm not sure why this fixes the crash.

Traceback (most recent call last):
  File "/Users/jp/Library/Application Support/Realm/rlm_lldb.py", line 226, in RLMResults_SummaryProvider
    if not is_results_evaluated(obj):
  File "/Users/jp/Library/Application Support/Realm/rlm_lldb.py", line 213, in is_results_evaluated
    mode_query_value = next(m for m in mode_type.enum_members if m.name == 'Query').GetValueAsUnsigned()
StopIteration
* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x0)
  * frame #0: 0x00007fffcebe8ae6 libobjc.A.dylib`lookUpImpOrForward + 79
    frame #1: 0x00007fffcebe85d4 libobjc.A.dylib`_objc_msgSend_uncached + 68
    frame #2: Realm`-[RLMResults deleteObjectsFromRealm]::$_14::operator(this=0x00007fff5fbfb8c8)() const at RLMResults.mm:424
    frame #3: Realm`auto translateErrors<-[RLMResults deleteObjectsFromRealm]::$_14>(f=0x00007fff5fbfb8c8, aggregateMethod=0x0000000000000000) at RLMResults.mm:108
    frame #4: Realm`::-[RLMResults deleteObjectsFromRealm](self=0x000000010230bb10, _cmd="deleteObjectsFromRealm") at RLMResults.mm:417
    frame #5: Realm`::-[RLMRealm deleteObjects:](self=0x00006080000a2ca0, _cmd="deleteObjects:", array=(None[0])) at RLMRealm.mm:623
    frame #6: RealmSwift`Realm.delete<A where ...> (objects=<unavailable>, self=0x0000608000030040) -> () at Realm.swift:404
    frame #7: RealmSwift Tests`RealmTests.(realm=0x0000608000030040) -> ()).(closure #1) at RealmTests.swift:435
    frame #8: RealmSwift`Realm.write(block=0x0000000104a35270 RealmSwift Tests`RealmSwift_Tests.RealmTests.(testDeleteResults () -> ()).(closure #1) at RealmTests.swift:430, self=0x0000608000030040, $error=Error @ 0x00007fff5fbfbe40) throws -> ()) throws -> () at Realm.swift:124
    frame #9: RealmSwift Tests`RealmTests.testDeleteResults(self=0x0000608000089fb0) -> () at RealmTests.swift:437
    frame #10: RealmSwift Tests`@objc RealmTests.testDeleteResults() -> () at RealmTests.swift:0
    frame #11: 0x00007fffb9f733ec CoreFoundation`__invoking___ + 140
    frame #12: 0x00007fffb9f73271 CoreFoundation`-[NSInvocation invoke] + 289
    frame #13: 0x00000001000c847c XCTest`__24-[XCTestCase invokeTest]_block_invoke.234 + 50
    frame #14: 0x000000010010dcd6 XCTest`-[XCTMemoryChecker _assertInvalidObjectsDeallocatedAfterScope:] + 37
    frame #15: 0x00000001000c8040 XCTest`__24-[XCTestCase invokeTest]_block_invoke_2 + 665
    frame #16: 0x0000000100105916 XCTest`-[XCTestContext performInScope:] + 190
    frame #17: 0x00000001000c7d94 XCTest`-[XCTestCase invokeTest] + 254
    frame #18: RealmSwift Tests`TestCase.(self=0x0000608000089fb0) -> ()).(closure #1) at TestCase.swift:79
    frame #19: RealmSwift Tests`thunk at TestCase.swift:0
    frame #20: RealmSwift Tests`partial apply for thunk at TestCase.swift:0
    frame #21: 0x00000001021ef5c8 libswiftObjectiveC.dylib`ObjectiveC.autoreleasepool <A> (invoking : () throws -> A) throws -> A + 56
    frame #22: RealmSwift Tests`TestCase.invokeTest(self=0x0000608000089fb0) -> () at TestCase.swift:79
    frame #23: RealmSwift Tests`@objc TestCase.invokeTest() -> () at TestCase.swift:0
    frame #24: 0x00000001000c8803 XCTest`-[XCTestCase performTest:] + 565
    frame #25: 0x00000001000c5776 XCTest`__27-[XCTestSuite performTest:]_block_invoke + 300
    frame #26: 0x00000001000c5366 XCTest`-[XCTestSuite _performProtectedSectionForTest:testSection:] + 29
    frame #27: 0x00000001000c554c XCTest`-[XCTestSuite performTest:] + 214
    frame #28: 0x00000001000c5776 XCTest`__27-[XCTestSuite performTest:]_block_invoke + 300
    frame #29: 0x00000001000c5366 XCTest`-[XCTestSuite _performProtectedSectionForTest:testSection:] + 29
    frame #30: 0x00000001000c554c XCTest`-[XCTestSuite performTest:] + 214
    frame #31: 0x00000001000c5776 XCTest`__27-[XCTestSuite performTest:]_block_invoke + 300
    frame #32: 0x00000001000c5366 XCTest`-[XCTestSuite _performProtectedSectionForTest:testSection:] + 29
    frame #33: 0x00000001000c554c XCTest`-[XCTestSuite performTest:] + 214
    frame #34: 0x000000010011883c XCTest`__44-[XCTTestRunSession runTestsAndReturnError:]_block_invoke + 40
    frame #35: 0x00000001000dbe0e XCTest`-[XCTestObservationCenter _observeTestExecutionForBlock:] + 587
    frame #36: 0x00000001001186da XCTest`-[XCTTestRunSession runTestsAndReturnError:] + 281
    frame #37: 0x00000001000b11fb XCTest`-[XCTestDriver runTestsAndReturnError:] + 254
    frame #38: 0x0000000100107fc9 XCTest`_XCTestMain + 773
    frame #39: 0x00007fffb9f957dc CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 12
    frame #40: 0x00007fffb9f767e4 CoreFoundation`__CFRunLoopDoBlocks + 356
    frame #41: 0x00007fffb9f75f65 CoreFoundation`__CFRunLoopRun + 917
    frame #42: 0x00007fffb9f75974 CoreFoundation`CFRunLoopRunSpecific + 420
    frame #43: 0x00007fffb9501a5c HIToolbox`RunCurrentEventLoopInMode + 240
    frame #44: 0x00007fffb9501799 HIToolbox`ReceiveNextEventCommon + 184
    frame #45: 0x00007fffb95016c6 HIToolbox`_BlockUntilNextEventMatchingListInModeWithFilter + 71
    frame #46: 0x00007fffb7aa75b4 AppKit`_DPSNextEvent + 1120
    frame #47: 0x00007fffb8221d6b AppKit`-[NSApplication(NSEvent) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] + 2789
    frame #48: 0x00007fffb7a9bf35 AppKit`-[NSApplication run] + 926
    frame #49: 0x00007fffb7a66850 AppKit`NSApplicationMain + 1237
    frame #50: TestHost`main(argc=5, argv=0x00007fff5fbfef58) at main.m:40
    frame #51: 0x00007fffcf4d9255 libdyld.dylib`start + 1
    frame #52: 0x00007fffcf4d9255 libdyld.dylib`start + 1

Realm/RLMResults.mm

@@ -414,15 +414,18 @@ - (id)averageOfProperty:(NSString *)property {
 }
 
 - (void)deleteObjectsFromRealm {
-    return translateErrors([&] {
+    try {
         if (_results.get_mode() == Results::Mode::Table) {
             RLMResultsValidateInWriteTransaction(self);
             RLMClearTable(*_info);
         }
         else {
             RLMTrackDeletions(_realm, ^{ _results.clear(); });
         }
-    });
+    }
+    catch (...) {
+        throwError(nil);
+    }
 }
 
 - (NSString *)description {