[CS] Use value() instead of * for ArgumentMismatchFailure

Make sure we reliably crash rather than producing garbage.

Author: hamishknight

lib/Sema/CSDiagnostics.h

@@ -2170,7 +2170,7 @@ class ArgumentMismatchFailure : public ContextualFailure {
                           FixBehavior fixBehavior =
                               FixBehavior::Error)
       : ContextualFailure(solution, argType, paramType, locator, fixBehavior),
-        Info(*getFunctionArgApplyInfo(getLocator())) {}
+        Info(getFunctionArgApplyInfo(getLocator()).value()) {}
 
   bool diagnoseAsError() override;
   bool diagnoseAsNote() override;