fix(promicro): exclude emoji to fit under the warm-store region

nrf52_promicro_diy_tcxo has been failing the nrf52 warm-region guard on
develop: the image ends at 0xEA0C0, 192 bytes past the 12 KB WarmNodeStore
record-ring reserved at 0xEA000. This variant compiles four radio driver
families (SX126x/LLCC68, SX127x/RF95, LR11x0/LR1121, LR2021) so any module
can be soldered on, which makes it the largest nrf52 image we ship.

Building it with -D EXCLUDE_EMOJI saves 6,808 bytes and puts the image at
0xE8618, 6.6 KB clear of the warm region.

EXCLUDE_EMOJI was not previously usable: graphics::emotes[] becomes empty,
but the canned-message emote picker never checked for that. Entering the
picker clamped emotePickerIndex to numEmotes - 1 (i.e. -1), and selecting
read emotes[-1].label into a String - an out-of-bounds read of whatever
precedes the array in flash. Guard both entry points instead: refuse to
open the picker when there are no emotes, and bounce back to freetext if
the picker state is somehow reached anyway.

Under whole-image LTO those guards fold to constants, so the picker draw
and input paths dead-strip entirely on builds that set EXCLUDE_EMOJI -
which is where the savings come from beyond the bitmap data itself.

Received messages containing emoji render as text on this variant, and
the emote-list key is a no-op. Verified rak4631 (emoji enabled) is
unaffected: 0xE46D8, 22 KB clear.

Author: thebentern

src/modules/CannedMessageModule.cpp

@@ -880,8 +880,10 @@ bool CannedMessageModule::handleFreeTextInput(const InputEvent *event)
     // All hardware keys fall through to here (CardKB, physical, etc.)
 
     if (event->kbchar == INPUT_BROKER_MSG_EMOTE_LIST) {
-        updateState(CANNED_MESSAGE_RUN_STATE_EMOTE_PICKER);
-        screen->forceDisplay();
+        if (graphics::numEmotes > 0) { // no picker on EXCLUDE_EMOJI builds (empty emotes[])
+            updateState(CANNED_MESSAGE_RUN_STATE_EMOTE_PICKER);
+            screen->forceDisplay();
+        }
         return true;
     }
     // Confirm select (Enter)
@@ -965,6 +967,11 @@ bool CannedMessageModule::handleFreeTextInput(const InputEvent *event)
 int CannedMessageModule::handleEmotePickerInput(const InputEvent *event)
 {
     int numEmotes = graphics::numEmotes;
+    if (numEmotes == 0) { // EXCLUDE_EMOJI: emotes[] is empty, any index would read out of bounds
+        updateState(CANNED_MESSAGE_RUN_STATE_FREETEXT, true);
+        screen->forceDisplay();
+        return 1;
+    }
 
     // Override isDown and isSelect ONLY for emote picker behavior
     bool isUp = isUpEvent(event);

variants/nrf52840/diy/nrf52_promicro_diy_tcxo/platformio.ini

@@ -15,6 +15,7 @@ board = promicro-nrf52840
 build_flags = ${nrf52840_base.build_flags}
   -I variants/nrf52840/diy/nrf52_promicro_diy_tcxo
   -D NRF52_PROMICRO_DIY
+  -D EXCLUDE_EMOJI ; this variant builds 4 radio driver families and is the largest nrf52 image; emote bitmaps don't fit under the 0xEA000 warm-store cap
 build_src_filter = ${nrf52_base.build_src_filter} +<../variants/nrf52840/diy/nrf52_promicro_diy_tcxo>
 debug_tool = jlink