prevent an infinite loop

[Fil]

The situation happens in force simulations when a point is horribly far (maybe because of a programming error, or because we set the wrong parameters on an experimental force). Then forceCollide calls quadtree(nodes, x,,y), which tries to cover by repeatedly doubling z=0. This ends up crashing the browser.

[Fil]

test:

tape("quadtree.cover() does not crash on huge values", function(test) {
  d3_quadtree.quadtree([[1e23, 0]]);
  test.end();
});

result:

<--- Last few GCs --->

[42466:0x103b14000]    11271 ms: Mark-sweep 1396.5 (1425.2) -> 1396.2 (1425.7) MB, 1207.9 / 0.0 ms  (+ 0.0 ms in 68 steps since start of marking, biggest step 0.0 ms, walltime since start of marking 1217 ms) (average mu = 0.162, current mu = 0.013) alloca[42466:0x103b14000]    12525 ms: Mark-sweep 1398.3 (1425.7) -> 1397.9 (1427.2) MB, 1251.7 / 0.0 ms  (average mu = 0.088, current mu = 0.002) allocation failure scavenge might not succeed


<--- JS stacktrace --->

==== JS stack trace =========================================

    0: ExitFrame [pc: 0xe6b825dbe3d]
Security context: 0x029c33e1e6e9 <JSObject>
    1: tree_cover [0x29c08a2d7e9] [/Users/fil/Sites/d3/d3-quadtree/dist/d3-quadtree.js:~93] [pc=0xe6b825e5b7e](this=0x029cfb3a69a9 <Quadtree map = 0x29c631185c9>,x=0x029cfb3a6999 <Number 1e+23>,y=0x029cfb3a6989 <Number 0>)
    2: addAll [0x29c08a2da29] [/Users/fil/Sites/d3/d3-quadtree/dist/d3-quadtree.js:83] [bytecode=0x29c08a4e929 offset=257](this=0x029cfb3a...

FATAL ERROR: Ineffective mark-compacts near heap limit Allocation failed - JavaScript heap out of memory
 1: 0x1009746b6 node::Abort() (.cold.1) [/usr/local/Cellar/node@10/10.16.3/bin/node]
 2: 0x10003b9d6 node_module_register [/usr/local/Cellar/node@10/10.16.3/bin/node]
 3: 0x10003bb97 node::OnFatalError(char const*, char const*) [/usr/local/Cellar/node@10/10.16.3/bin/node]
 4: 0x100178c5b v8::Utils::ReportOOMFailure(v8::internal::Isolate*, char const*, bool) [/usr/local/Cellar/node@10/10.16.3/bin/node]
 5: 0x100178bfd v8::internal::V8::FatalProcessOutOfMemory(v8::internal::Isolate*, char const*, bool) [/usr/local/Cellar/node@10/10.16.3/bin/node]
 6: 0x10042d170 v8::internal::Heap::UpdateSurvivalStatistics(int) [/usr/local/Cellar/node@10/10.16.3/bin/node]
 7: 0x10042edad v8::internal::Heap::CheckIneffectiveMarkCompact(unsigned long, double) [/usr/local/Cellar/node@10/10.16.3/bin/node]
 8: 0x10042c44a v8::internal::Heap::PerformGarbageCollection(v8::internal::GarbageCollector, v8::GCCallbackFlags) [/usr/local/Cellar/node@10/10.16.3/bin/node]
 9: 0x10042b25b v8::internal::Heap::CollectGarbage(v8::internal::AllocationSpace, v8::internal::GarbageCollectionReason, v8::GCCallbackFlags) [/usr/local/Cellar/node@10/10.16.3/bin/node]
10: 0x100433882 v8::internal::Heap::AllocateRawWithLigthRetry(int, v8::internal::AllocationSpace, v8::internal::AllocationAlignment) [/usr/local/Cellar/node@10/10.16.3/bin/node]
11: 0x1004338cc v8::internal::Heap::AllocateRawWithRetryOrFail(int, v8::internal::AllocationSpace, v8::internal::AllocationAlignment) [/usr/local/Cellar/node@10/10.16.3/bin/node]
12: 0x1004141bb v8::internal::Factory::NewFillerObject(int, bool, v8::internal::AllocationSpace) [/usr/local/Cellar/node@10/10.16.3/bin/node]
13: 0x1005ee4e1 v8::internal::Runtime_AllocateInNewSpace(int, v8::internal::Object**, v8::internal::Isolate*) [/usr/local/Cellar/node@10/10.16.3/bin/node]
14: 0xe6b825dbe3d