Fix invalid parts linkage in assemblies when the folder has only one …

…char.

Fix a bug in the `Split` function that would drop a single character
directory name at the end of the path.

Because of the above bug when a directory containing an assembly file had
a name with only one character, the assembly file was saved incorrectly and
the path to the linked files was invalid.

For example if `assembly.slvs` was located in a directory called `a` and
links `subpart.slvs` in the same directory this would result in:

Group.impFileRel=a\subpart.slvs

Which resulted in the linked part not being found when opening next time.

Fixes: solvespace#1347

src/platform/platform.cpp

@@ -93,9 +93,7 @@ static std::vector<std::string> Split(const std::string &joined, char separator)
         pos += 1;
     }
 
-    if(oldpos != joined.length() - 1) {
-        parts.push_back(joined.substr(oldpos));
-    }
+    parts.push_back(joined.substr(oldpos));
 
     return parts;
 }