results: fix non-void [] overload

stew/byteutils.nim

@@ -46,7 +46,7 @@ proc readHexChar*(c: char): byte {.noSideEffect, inline.}=
   of 'a'..'f': result = byte(ord(c) - ord('a') + 10)
   of 'A'..'F': result = byte(ord(c) - ord('A') + 10)
   else:
-    raise newException(ValueError, $c & "is not a hexademical character")
+    raise newException(ValueError, $c & " is not a hexademical character")
 
 template skip0xPrefix(hexStr: string): int =
   ## Returns the index of the first meaningful char in `hexStr` by skipping

stew/results.nim

@@ -453,7 +453,7 @@ func get*[T, E](self: var Result[T, E]): var T {.inline.} =
   assertOk(self)
   self.v
 
-template `[]`*[T, E](self: Result[T, E]): T =
+template `[]`*[T: not void, E](self: Result[T, E]): T =
   ## Fetch value of result if set, or raise Defect
   ## Exception bridge mode: raise given Exception instead
   mixin get