Fix problems caused by b411d20

Also add the test case from #1536 so we can be sure things stay correct.

pipenv/patched/prettytoml/elements/traversal/__init__.py

@@ -76,7 +76,7 @@ class TraversalMixin:
         following_comment = self._find_following_comment(index)
         following_newline = self._find_following_newline(index)
 
-        if following_comment == float('inf'):
+        if following_comment == float('-inf'):
             return following_newline
         if following_newline == float('-inf'):
             return following_comment

tests/test_vendor.py

@@ -0,0 +1,31 @@
+# Make sure we use the patched packages.
+import pipenv   # noqa
+
+from prettytoml import lexer
+from prettytoml.elements.atomic import AtomicElement
+from prettytoml.elements.metadata import (
+    WhitespaceElement, PunctuationElement, CommentElement,
+)
+from prettytoml.elements.table import TableElement
+
+
+def test_table():
+
+    initial_toml = """id=42 # My id\nage=14"""
+    tokens = tuple(lexer.tokenize(initial_toml))
+    table = TableElement([
+        AtomicElement(tokens[0:1]),
+        PunctuationElement(tokens[1:2]),
+        AtomicElement(tokens[2:3]),
+        WhitespaceElement(tokens[3:4]),
+        CommentElement(tokens[4:6]),
+
+        AtomicElement(tokens[6:7]),
+        PunctuationElement(tokens[7:8]),
+        AtomicElement(tokens[8:9]),
+    ])
+
+    assert set(table.items()) == {('id', 42), ('age', 14)}
+
+    del table['id']
+    assert set(table.items()) == {('age', 14)}