Workaround for multiple `waitFor` where `await` must be used.

Bump version to 2.0.7.

asyncdispatch2.nimble

@@ -1,5 +1,5 @@
 packageName   = "asyncdispatch2"
-version       = "2.0.6"
+version       = "2.0.7"
 author        = "Status Research & Development GmbH"
 description   = "Asyncdispatch2"
 license       = "Apache License 2.0 or MIT"

asyncdispatch2/asyncloop.nim

@@ -227,6 +227,12 @@ template processTimers(loop: untyped) =
 template processCallbacks(loop: untyped) =
   var count = len(loop.callbacks)
   for i in 0..<count:
+    # This is mostly workaround for people which are using `waitFor` where
+    # it must be used `await`. While using `waitFor` inside of callbacks
+    # dispatcher's callback list is got decreased and length of
+    # `loop.callbacks` become not equal to `count`, its why `IndexError`
+    # can be generated.
+    if len(loop.callbacks) == 0: break
     let callable = loop.callbacks.popFirst()
     callable.function(callable.udata)