Fix disabling wxStaticText repeatedly in wxOSX.

Changes in r78107 would reset control's color to gray if it was disabled
more than once in a row. Guard against this and only remember the color
of an enabled control.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@78144 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/osx/cocoa/stattext.mm

@@ -56,6 +56,8 @@
 
 - (void) setEnabled:(BOOL) flag 
 {
+    bool wasEnabled = [self isEnabled];
+
     [super setEnabled: flag]; 
     
     if (![self drawsBackground]) { 
@@ -68,9 +70,12 @@
                 [self setTextColor: m_textColor];
         }
         else 
+        {
+            if (wasEnabled)
             {
                 [m_textColor release];
                 m_textColor = [[self textColor] retain];
+            }
             [self setTextColor: [NSColor secondarySelectedControlColor]]; 
         } 
     }