Don't use "object" as fallback return type in Google and Numpy docstrings

Because it breaks code insight otherwise. Type "object" is not the
same thing as "Any", and the latter isn't fully supported in PyCharm
yet. As a temporary solution insert empty line under "Returns" section
instead.

python/src/com/jetbrains/python/documentation/docstrings/PyDocstringGenerator.java

@@ -441,8 +441,8 @@ public class PyDocstringGenerator {
         sectionBuilder.startReturnsSection();
         boolean hasTypedReturns = false;
         for (DocstringParam returnValue : returnValues) {
-          if (returnValue.getType() != null) {
-            sectionBuilder.addReturnValue(null, getDefaultType(returnValue), "");
+          if (StringUtil.isNotEmpty(returnValue.getType())) {
+            sectionBuilder.addReturnValue(null, returnValue.getType(), "");
             hasTypedReturns = true;
           }
         }

python/testData/intentions/afterGoogleDocStubWithTypes.py

@@ -6,6 +6,6 @@ def f(x, y):
       y ():
 
     Returns:
-      object:
+
     """
     return 42

python/testData/intentions/afterNumpyDocStubWithTypes.py

@@ -8,6 +8,6 @@ def f(x, y):
 
     Returns
     -------
-    object
+
     """
     return 42