[concept.booleantestable] Use tie before cross references

opensdh · zygoloid · commit a48408f12ad8 · 2020-03-24T16:16:54.000-07:00
diff --git a/source/concepts.tex b/source/concepts.tex
@@ -846,7 +846,7 @@
 The exposition-only \exposconcept{boolean-testable} concept
 specifies the requirements on expressions
 that are convertible to \tcode{bool} and
-for which the logical operators
+for which the logical operators~%
 (\ref{expr.log.and}, \ref{expr.log.or}, \ref{expr.unary.op})
 have the conventional semantics.
 
